diff --git a/example/custom/query/main.py b/example/custom/query/main.py
new file mode 100644
index 00000000..ec87214a
--- /dev/null
+++ b/example/custom/query/main.py
@@ -0,0 +1,49 @@
+from cpl.core.console import Console
+from cpl.core.utils.benchmark import Benchmark
+from cpl.query.collection import Collection
+from cpl.query.enumerable import Enumerable
+from cpl.query.list import List
+from cpl.query.immutable_list import ImmutableList
+from cpl.query.set import Set
+
+
+def _default():
+    Console.write_line(Enumerable.empty().to_list())
+
+    Console.write_line(Enumerable.range(0, 100).length)
+    Console.write_line(Enumerable.range(0, 100).to_list())
+
+    Console.write_line(Enumerable.range(0, 100).where(lambda x: x % 2 == 0).length)
+    Console.write_line(
+        Enumerable.range(0, 100).where(lambda x: x % 2 == 0).to_list().select(lambda x: str(x)).to_list()
+    )
+    Console.write_line(List)
+
+    s =Enumerable.range(0, 10).to_set()
+    Console.write_line(s)
+    s.add(1)
+    Console.write_line(s)
+
+
+def t_benchmark(data: list):
+    Benchmark.all("Enumerable", lambda: Enumerable(data).where(lambda x: x % 2 == 0).select(lambda x: x * 2).to_list())
+    Benchmark.all("Set", lambda: Set(data).where(lambda x: x % 2 == 0).select(lambda x: x * 2).to_list())
+    Benchmark.all("Collection", lambda: Collection(data).where(lambda x: x % 2 == 0).select(lambda x: x * 2).to_list())
+    Benchmark.all("List", lambda: List(data).where(lambda x: x % 2 == 0).select(lambda x: x * 2).to_list())
+    Benchmark.all(
+        "ImmutableList", lambda: ImmutableList(data).where(lambda x: x % 2 == 0).select(lambda x: x * 2).to_list()
+    )
+    Benchmark.all("List comprehension", lambda: [x * 2 for x in data if x % 2 == 0])
+
+
+def main():
+    N = 10_000_000
+    data = list(range(N))
+    t_benchmark(data)
+
+    Console.write_line()
+    _default()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/src/cpl-core/cpl/core/typing.py b/src/cpl-core/cpl/core/typing.py
index b0a980a3..c843fa2b 100644
--- a/src/cpl-core/cpl/core/typing.py
+++ b/src/cpl-core/cpl/core/typing.py
@@ -14,3 +14,4 @@ UuidId = str | UUID
 SerialId = int
 
 Id = UuidId | SerialId
+TNumber = int | float | complex
diff --git a/src/cpl-core/cpl/core/utils/benchmark.py b/src/cpl-core/cpl/core/utils/benchmark.py
new file mode 100644
index 00000000..f9d41bc8
--- /dev/null
+++ b/src/cpl-core/cpl/core/utils/benchmark.py
@@ -0,0 +1,57 @@
+import time
+import tracemalloc
+from typing import List, Callable
+
+from cpl.core.console import Console
+
+
+class Benchmark:
+
+    @staticmethod
+    def all(label: str, func: Callable, iterations: int = 5):
+        times: List[float] = []
+        mems: List[float] = []
+
+        for _ in range(iterations):
+            start = time.perf_counter()
+            func()
+            end = time.perf_counter()
+            times.append(end - start)
+
+        for _ in range(iterations):
+            tracemalloc.start()
+            func()
+            current, peak = tracemalloc.get_traced_memory()
+            tracemalloc.stop()
+            mems.append(peak)
+
+        avg_time = sum(times) / len(times)
+        avg_mem = sum(mems) / len(mems) / (1024 * 1024)
+        Console.write_line(f"{label:20s} -> min {min(times):.6f}s  avg {avg_time:.6f}s  mem {avg_mem:.8f} MB")
+
+    @staticmethod
+    def time(label: str, func: Callable, iterations: int = 5):
+        times: List[float] = []
+
+        for _ in range(iterations):
+            start = time.perf_counter()
+            func()
+            end = time.perf_counter()
+            times.append(end - start)
+
+        avg_time = sum(times) / len(times)
+        Console.write_line(f"{label:20s} -> min {min(times):.6f}s  avg {avg_time:.6f}s")
+
+    @staticmethod
+    def memory(label: str, func: Callable, iterations: int = 5):
+        mems: List[float] = []
+
+        for _ in range(iterations):
+            tracemalloc.start()
+            func()
+            current, peak = tracemalloc.get_traced_memory()
+            tracemalloc.stop()
+            mems.append(peak)
+
+        avg_mem = sum(mems) / len(mems) / (1024 * 1024)
+        Console.write_line(f"{label:20s} -> mem {avg_mem:.2f} MB")
diff --git a/src/cpl-core/cpl/core/utils/number.py b/src/cpl-core/cpl/core/utils/number.py
new file mode 100644
index 00000000..33284ea5
--- /dev/null
+++ b/src/cpl-core/cpl/core/utils/number.py
@@ -0,0 +1,48 @@
+from typing import Any
+
+
+class Number:
+
+    @staticmethod
+    def is_number(value: Any) -> bool:
+        """Check if the value is a number (int or float)."""
+        return isinstance(value, (int, float, complex))
+
+    @staticmethod
+    def to_number(value: Any) -> int | float | complex:
+        """
+        Convert a given value into int, float, or complex.
+        Raises ValueError if conversion is not possible.
+        """
+
+        if isinstance(value, (int, float, complex)):
+            return value
+
+        if isinstance(value, str):
+            value = value.strip()
+            for caster in (int, float, complex):
+                try:
+                    return caster(value)
+                except ValueError:
+                    continue
+            raise ValueError(f"Cannot convert string '{value}' to number.")
+
+        if isinstance(value, bool):
+            return int(value)
+
+        try:
+            return int(value)
+        except Exception:
+            pass
+
+        try:
+            return float(value)
+        except Exception:
+            pass
+
+        try:
+            return complex(value)
+        except Exception:
+            pass
+
+        raise ValueError(f"Cannot convert type {type(value)} to number.")
diff --git a/src/cpl-query/cpl/query/_helper.py b/src/cpl-query/cpl/query/_helper.py
deleted file mode 100644
index 6f92e585..00000000
--- a/src/cpl-query/cpl/query/_helper.py
+++ /dev/null
@@ -1,2 +0,0 @@
-def is_number(t: type) -> bool:
-    return issubclass(t, int) or issubclass(t, float) or issubclass(t, complex)
diff --git a/src/cpl-query/cpl/query/base/__init__.py b/src/cpl-query/cpl/query/base/__init__.py
deleted file mode 100644
index 97de7598..00000000
--- a/src/cpl-query/cpl/query/base/__init__.py
+++ /dev/null
@@ -1,5 +0,0 @@
-from .default_lambda import default_lambda
-from .ordered_queryable import OrderedQueryable
-from .sequence import Sequence
-from .ordered_queryable_abc import OrderedQueryableABC
-from .queryable_abc import QueryableABC
diff --git a/src/cpl-query/cpl/query/base/default_lambda.py b/src/cpl-query/cpl/query/base/default_lambda.py
deleted file mode 100644
index 3d985ff2..00000000
--- a/src/cpl-query/cpl/query/base/default_lambda.py
+++ /dev/null
@@ -1,2 +0,0 @@
-def default_lambda(x: object):
-    return x
diff --git a/src/cpl-query/cpl/query/base/ordered_queryable.py b/src/cpl-query/cpl/query/base/ordered_queryable.py
deleted file mode 100644
index 5788e0e8..00000000
--- a/src/cpl-query/cpl/query/base/ordered_queryable.py
+++ /dev/null
@@ -1,34 +0,0 @@
-from collections.abc import Callable
-
-from cpl.query.base.ordered_queryable_abc import OrderedQueryableABC
-from cpl.query.exceptions import ArgumentNoneException, ExceptionArgument
-
-
-class OrderedQueryable(OrderedQueryableABC):
-    r"""Implementation of :class: `cpl.query.base.ordered_queryable_abc.OrderedQueryableABC`"""
-
-    def __init__(self, _t: type, _values: OrderedQueryableABC = None, _func: Callable = None):
-        OrderedQueryableABC.__init__(self, _t, _values, _func)
-
-    def then_by(self, _func: Callable) -> OrderedQueryableABC:
-        if self is None:
-            raise ArgumentNoneException(ExceptionArgument.list)
-
-        if _func is None:
-            raise ArgumentNoneException(ExceptionArgument.func)
-
-        self._funcs.append(_func)
-
-        return OrderedQueryable(self.type, sorted(self, key=lambda *args: [f(*args) for f in self._funcs]), _func)
-
-    def then_by_descending(self, _func: Callable) -> OrderedQueryableABC:
-        if self is None:
-            raise ArgumentNoneException(ExceptionArgument.list)
-
-        if _func is None:
-            raise ArgumentNoneException(ExceptionArgument.func)
-
-        self._funcs.append(_func)
-        return OrderedQueryable(
-            self.type, sorted(self, key=lambda *args: [f(*args) for f in self._funcs], reverse=True), _func
-        )
diff --git a/src/cpl-query/cpl/query/base/ordered_queryable_abc.py b/src/cpl-query/cpl/query/base/ordered_queryable_abc.py
deleted file mode 100644
index a11d9796..00000000
--- a/src/cpl-query/cpl/query/base/ordered_queryable_abc.py
+++ /dev/null
@@ -1,38 +0,0 @@
-from __future__ import annotations
-
-from abc import abstractmethod
-from collections.abc import Callable
-from typing import Iterable
-
-from cpl.query.base.queryable_abc import QueryableABC
-
-
-class OrderedQueryableABC(QueryableABC):
-    @abstractmethod
-    def __init__(self, _t: type, _values: Iterable = None, _func: Callable = None):
-        QueryableABC.__init__(self, _t, _values)
-        self._funcs: list[Callable] = []
-        if _func is not None:
-            self._funcs.append(_func)
-
-    @abstractmethod
-    def then_by(self, func: Callable) -> OrderedQueryableABC:
-        r"""Sorts OrderedList in ascending order by function
-
-        Parameter:
-            func: :class:`Callable`
-
-        Returns:
-            list of :class:`cpl.query.base.ordered_queryable_abc.OrderedQueryableABC`
-        """
-
-    @abstractmethod
-    def then_by_descending(self, func: Callable) -> OrderedQueryableABC:
-        r"""Sorts OrderedList in descending order by function
-
-        Parameter:
-            func: :class:`Callable`
-
-        Returns:
-            list of :class:`cpl.query.base.ordered_queryable_abc.OrderedQueryableABC`
-        """
diff --git a/src/cpl-query/cpl/query/base/queryable_abc.py b/src/cpl-query/cpl/query/base/queryable_abc.py
deleted file mode 100644
index aff56af9..00000000
--- a/src/cpl-query/cpl/query/base/queryable_abc.py
+++ /dev/null
@@ -1,569 +0,0 @@
-from __future__ import annotations
-
-from typing import Optional, Callable, Union, Iterable, Any
-
-from cpl.query._helper import is_number
-from cpl.query.base import default_lambda
-from cpl.query.base.sequence import Sequence
-from cpl.query.exceptions import (
-    InvalidTypeException,
-    ArgumentNoneException,
-    ExceptionArgument,
-    IndexOutOfRangeException,
-)
-
-
-class QueryableABC(Sequence):
-    def __init__(self, t: type, values: Iterable = None):
-        Sequence.__init__(self, t, values)
-
-    def all(self, _func: Callable = None) -> bool:
-        r"""Checks if every element of list equals result found by function
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            bool
-        """
-        if _func is None:
-            _func = default_lambda
-
-        return self.count(_func) == self.count()
-
-    def any(self, _func: Callable = None) -> bool:
-        r"""Checks if list contains result found by function
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            bool
-        """
-        if _func is None:
-            _func = default_lambda
-
-        return self.where(_func).count() > 0
-
-    def average(self, _func: Callable = None) -> Union[int, float, complex]:
-        r"""Returns average value of list
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            Union[int, float, complex]
-        """
-        if _func is None and not is_number(self.type):
-            raise InvalidTypeException()
-
-        return self.sum(_func) / self.count()
-
-    def contains(self, _value: object) -> bool:
-        r"""Checks if list contains value given by function
-
-        Parameter
-        ---------
-            value: :class:`object`
-                value
-
-        Returns
-        -------
-            bool
-        """
-        if _value is None:
-            raise ArgumentNoneException(ExceptionArgument.value)
-
-        return self.where(lambda x: x == _value).count() > 0
-
-    def count(self, _func: Callable = None) -> int:
-        r"""Returns length of list or count of found elements
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            int
-        """
-        if _func is None:
-            return self.__len__()
-
-        return self.where(_func).count()
-
-    def distinct(self, _func: Callable = None) -> QueryableABC:
-        r"""Returns list without redundancies
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        if _func is None:
-            _func = default_lambda
-
-        result = []
-        known_values = []
-        for element in self:
-            value = _func(element)
-            if value in known_values:
-                continue
-
-            known_values.append(value)
-            result.append(element)
-
-        return type(self)(self._type, result)
-
-    def element_at(self, _index: int) -> any:
-        r"""Returns element at given index
-
-        Parameter
-        ---------
-            _index: :class:`int`
-                index
-
-        Returns
-        -------
-            Value at _index: any
-        """
-        if _index is None:
-            raise ArgumentNoneException(ExceptionArgument.index)
-
-        if _index < 0 or _index >= self.count():
-            raise IndexOutOfRangeException
-
-        result = self._values[_index]
-        if result is None:
-            raise IndexOutOfRangeException
-
-        return result
-
-    def element_at_or_default(self, _index: int) -> Optional[any]:
-        r"""Returns element at given index or None
-
-        Parameter
-        ---------
-            _index: :class:`int`
-                index
-
-        Returns
-        -------
-            Value at _index: Optional[any]
-        """
-        if _index is None:
-            raise ArgumentNoneException(ExceptionArgument.index)
-
-        try:
-            return self._values[_index]
-        except IndexError:
-            return None
-
-    def first(self) -> any:
-        r"""Returns first element
-
-        Returns
-        -------
-            First element of list: any
-        """
-        if self.count() == 0:
-            raise IndexOutOfRangeException()
-
-        return self._values[0]
-
-    def first_or_default(self) -> any:
-        r"""Returns first element or None
-
-        Returns
-        -------
-            First element of list: Optional[any]
-        """
-        if self.count() == 0:
-            return None
-
-        return self._values[0]
-
-    def for_each(self, _func: Callable = None):
-        r"""Runs given function for each element of list
-
-        Parameter
-        ---------
-            func: :class: `Callable`
-                function to call
-        """
-        if _func is not None:
-            for element in self:
-                _func(element)
-
-        return self
-
-    def group_by(self, _func: Callable = None) -> QueryableABC:
-        r"""Groups by func
-
-        Returns
-        -------
-            Grouped list[list[any]]: any
-        """
-        if _func is None:
-            _func = default_lambda
-        groups = {}
-
-        for v in self:
-            value = _func(v)
-            if v not in groups:
-                groups[value] = []
-
-            groups[value].append(v)
-
-        v = []
-        for g in groups.values():
-            v.append(type(self)(object, g))
-        x = type(self)(type(self), v)
-        return x
-
-    def last(self) -> any:
-        r"""Returns last element
-
-        Returns
-        -------
-            Last element of list: any
-        """
-        if self.count() == 0:
-            raise IndexOutOfRangeException()
-
-        return self._values[self.count() - 1]
-
-    def last_or_default(self) -> any:
-        r"""Returns last element or None
-
-        Returns
-        -------
-            Last element of list: Optional[any]
-        """
-        if self.count() == 0:
-            return None
-
-        return self._values[self.count() - 1]
-
-    def max(self, _func: Callable = None) -> object:
-        r"""Returns the highest value
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            object
-        """
-        if _func is None and not is_number(self.type):
-            raise InvalidTypeException()
-
-        if _func is None:
-            _func = default_lambda
-
-        return _func(max(self, key=_func))
-
-    def median(self, _func=None) -> Union[int, float]:
-        r"""Return the median value of data elements
-
-        Returns
-        -------
-            Union[int, float]
-        """
-        if _func is None:
-            _func = default_lambda
-
-        result = self.order_by(_func).select(_func).to_list()
-        length = len(result)
-        i = int(length / 2)
-        return result[i] if length % 2 == 1 else (float(result[i - 1]) + float(result[i])) / float(2)
-
-    def min(self, _func: Callable = None) -> object:
-        r"""Returns the lowest value
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            object
-        """
-        if _func is None and not is_number(self.type):
-            raise InvalidTypeException()
-
-        if _func is None:
-            _func = default_lambda
-
-        return _func(min(self, key=_func))
-
-    def order_by(self, _func: Callable = None) -> "OrderedQueryableABC":
-        r"""Sorts elements by function in ascending order
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            :class: `cpl.query.base.ordered_queryable_abc.OrderedQueryableABC`
-        """
-        if _func is None:
-            _func = default_lambda
-
-        from cpl.query.base.ordered_queryable import OrderedQueryable
-
-        return OrderedQueryable(self.type, sorted(self, key=_func), _func)
-
-    def order_by_descending(self, _func: Callable = None) -> "OrderedQueryableABC":
-        r"""Sorts elements by function in descending order
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            :class: `cpl.query.base.ordered_queryable_abc.OrderedQueryableABC`
-        """
-        if _func is None:
-            _func = default_lambda
-
-        from cpl.query.base.ordered_queryable import OrderedQueryable
-
-        return OrderedQueryable(self.type, sorted(self, key=_func, reverse=True), _func)
-
-    def reverse(self) -> QueryableABC:
-        r"""Reverses list
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        return type(self)(self._type, reversed(self._values))
-
-    def select(self, _func: Callable) -> QueryableABC:
-        r"""Formats each element of list to a given format
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        if _func is None:
-            _func = default_lambda
-
-        _l = [_func(_o) for _o in self]
-        _t = type(_l[0]) if len(_l) > 0 else Any
-
-        return type(self)(_t, _l)
-
-    def select_many(self, _func: Callable) -> QueryableABC:
-        r"""Flattens resulting lists to one
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        # The line below is pain. I don't understand anything of it...
-        # written on 09.11.2022 by Sven Heidemann
-        return type(self)(object, [_a for _o in self for _a in _func(_o)])
-
-    def single(self) -> any:
-        r"""Returns one single element of list
-
-        Returns
-        -------
-            Found value: any
-
-        Raises
-        ------
-            ArgumentNoneException: when argument is None
-            Exception: when argument is None or found more than one element
-        """
-        if self.count() > 1:
-            raise Exception("Found more than one element")
-        elif self.count() == 0:
-            raise Exception("Found no element")
-
-        return self._values[0]
-
-    def single_or_default(self) -> Optional[any]:
-        r"""Returns one single element of list
-
-        Returns
-        -------
-            Found value: Optional[any]
-        """
-        if self.count() > 1:
-            raise Exception("Index out of range")
-        elif self.count() == 0:
-            return None
-
-        return self._values[0]
-
-    def skip(self, _index: int) -> QueryableABC:
-        r"""Skips all elements from index
-
-        Parameter
-        ---------
-            _index: :class:`int`
-                index
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        if _index is None:
-            raise ArgumentNoneException(ExceptionArgument.index)
-
-        return type(self)(self.type, self._values[_index:])
-
-    def skip_last(self, _index: int) -> QueryableABC:
-        r"""Skips all elements after index
-
-        Parameter
-        ---------
-            _index: :class:`int`
-                index
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        if _index is None:
-            raise ArgumentNoneException(ExceptionArgument.index)
-
-        index = self.count() - _index
-        return type(self)(self._type, self._values[:index])
-
-    def sum(self, _func: Callable = None) -> Union[int, float, complex]:
-        r"""Sum of all values
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            Union[int, float, complex]
-        """
-        if _func is None and not is_number(self.type):
-            raise InvalidTypeException()
-
-        if _func is None:
-            _func = default_lambda
-
-        result = 0
-        for x in self:
-            result += _func(x)
-
-        return result
-
-    def split(self, _func: Callable) -> QueryableABC:
-        r"""Splits the list by given function
-
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                seperator
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        groups = []
-        group = []
-        for x in self:
-            v = _func(x)
-            if x == v:
-                groups.append(group)
-                group = []
-
-            group.append(x)
-
-        groups.append(group)
-
-        query_groups = []
-        for g in groups:
-            if len(g) == 0:
-                continue
-            query_groups.append(type(self)(self._type, g))
-
-        return type(self)(self._type, query_groups)
-
-    def take(self, _index: int) -> QueryableABC:
-        r"""Takes all elements from index
-
-        Parameter
-        ---------
-            _index: :class:`int`
-                index
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        if _index is None:
-            raise ArgumentNoneException(ExceptionArgument.index)
-
-        return type(self)(self._type, self._values[:_index])
-
-    def take_last(self, _index: int) -> QueryableABC:
-        r"""Takes all elements after index
-
-        Parameter
-        ---------
-            _index: :class:`int`
-                index
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        index = self.count() - _index
-
-        if index >= self.count() or index < 0:
-            raise IndexOutOfRangeException()
-
-        return type(self)(self._type, self._values[index:])
-
-    def where(self, _func: Callable = None) -> QueryableABC:
-        r"""Select element by function
-
-        Parameter
-        ---------
-            func: :class:`Callable`
-                selected value
-
-        Returns
-        -------
-            :class: `cpl.query.base.queryable_abc.QueryableABC`
-        """
-        if _func is None:
-            raise ArgumentNoneException(ExceptionArgument.func)
-
-        if _func is None:
-            _func = default_lambda
-
-        return type(self)(self.type, filter(_func, self))
diff --git a/src/cpl-query/cpl/query/base/sequence.py b/src/cpl-query/cpl/query/base/sequence.py
deleted file mode 100644
index 5eb349b5..00000000
--- a/src/cpl-query/cpl/query/base/sequence.py
+++ /dev/null
@@ -1,96 +0,0 @@
-from abc import abstractmethod, ABC
-from typing import Iterable
-
-
-class Sequence(ABC):
-    @abstractmethod
-    def __init__(self, t: type, values: Iterable = None):
-        assert t is not None
-        assert isinstance(t, type) or t == any
-        assert values is None or isinstance(values, Iterable)
-
-        if values is None:
-            values = []
-
-        self._values = list(values)
-
-        if t is None:
-            t = object
-
-        self._type = t
-
-    def __iter__(self):
-        return iter(self._values)
-
-    def __next__(self):
-        return next(iter(self._values))
-
-    def __len__(self):
-        return self.to_list().__len__()
-
-    @classmethod
-    def __class_getitem__(cls, _t: type) -> type:
-        return _t
-
-    def __repr__(self):
-        return f"<{type(self).__name__} {self.to_list().__repr__()}>"
-
-    @property
-    def type(self) -> type:
-        return self._type
-
-    def _check_type(self, __object: any):
-        if self._type == any:
-            return
-
-        if (
-            self._type is not None
-            and type(__object) != self._type
-            and not isinstance(type(__object), self._type)
-            and not issubclass(type(__object), self._type)
-        ):
-            raise Exception(f"Unexpected type: {type(__object)}\nExpected type: {self._type}")
-
-    def to_list(self) -> list:
-        r"""Converts :class: `cpl.query.base.sequence_abc.SequenceABC` to :class: `list`
-
-        Returns:
-            :class: `list`
-        """
-        return [x for x in self._values]
-
-    def copy(self) -> "Sequence":
-        r"""Creates a copy of sequence
-
-        Returns:
-            Sequence
-        """
-        return type(self)(self._type, self.to_list())
-
-    @classmethod
-    def empty(cls) -> "Sequence":
-        r"""Returns an empty sequence
-
-        Returns:
-            Sequence object that contains no elements
-        """
-        return cls(object, [])
-
-    def index_of(self, _object: object) -> int:
-        r"""Returns the index of given element
-
-        Returns:
-            Index of object
-
-        Raises:
-            IndexError if object not in sequence
-        """
-        for i, o in enumerate(self):
-            if o == _object:
-                return i
-
-        raise IndexError
-
-    @classmethod
-    def range(cls, start: int, length: int) -> "Sequence":
-        return cls(int, range(start, length))
diff --git a/src/cpl-query/cpl/query/collection.py b/src/cpl-query/cpl/query/collection.py
new file mode 100644
index 00000000..51133a13
--- /dev/null
+++ b/src/cpl-query/cpl/query/collection.py
@@ -0,0 +1,173 @@
+from itertools import islice, groupby
+from typing import Generic, Callable, Iterable, Iterator, Dict, Tuple, Optional
+
+from cpl.core.typing import T, R
+from cpl.query.list import List
+from cpl.query.typing import Predicate, K, Selector
+
+
+class Collection(Generic[T]):
+    def __init__(self, source: Iterable[T]):
+        self._source = source
+
+    def __iter__(self) -> Iterator[T]:
+        return iter(self._source)
+
+    @property
+    def length(self) -> int:
+        return sum(1 for _ in self._source)
+
+    def where(self, f: Predicate) -> "Collection[T]":
+        return Collection([x for x in self._source if f(x)])
+
+    def select(self, f: Selector) -> "Collection[R]":
+        return Collection([f(x) for x in self._source])
+
+    def select_many(self, f: Callable[[T], Iterable[R]]) -> "Collection[R]":
+        return Collection([y for x in self._source for y in f(x)])
+
+    def take(self, count: int) -> "Collection[T]":
+        return Collection(islice(self._source, count))
+
+    def skip(self, count: int) -> "Collection[T]":
+        return Collection(islice(self._source, count, None))
+
+    def take_while(self, f: Predicate) -> "Collection[T]":
+        result = []
+        for x in self._source:
+            if f(x):
+                result.append(x)
+            else:
+                break
+        return Collection(result)
+
+    def skip_while(self, f: Predicate) -> "Collection[T]":
+        it = iter(self._source)
+        for x in it:
+            if not f(x):
+                return Collection([x] + list(it))
+        return Collection([])
+
+    def distinct(self) -> "Collection[T]":
+        seen = set()
+        return Collection([x for x in self._source if not (x in seen or seen.add(x))])
+
+    def union(self, other: Iterable[T]) -> "Collection[T]":
+        return self.concat(other).distinct()
+
+    def intersect(self, other: Iterable[T]) -> "Collection[T]":
+        other_set = set(other)
+        return Collection([x for x in self._source if x in other_set])
+
+    def except_(self, other: Iterable[T]) -> "Collection[T]":
+        other_set = set(other)
+        return Collection([x for x in self._source if x not in other_set])
+
+    def concat(self, other: Iterable[T]) -> "Collection[T]":
+        return Collection(self._source) + list(other)
+
+    def count(self) -> int:
+        return len(list(self._source))
+
+    def sum(self, f: Optional[Selector] = None) -> R:
+        return sum([f(x) for x in self._source]) if f else sum(self._source)  # type: ignore
+
+    def min(self, f: Optional[Selector] = None) -> R:
+        return min([f(x) for x in self._source]) if f else min(self._source)  # type: ignore
+
+    def max(self, f: Optional[Selector] = None) -> R:
+        return max([f(x) for x in self._source]) if f else max(self._source)  # type: ignore
+
+    def average(self, f: Optional[Callable[[T], float]] = None) -> float:
+        values = [f(x) for x in self._source] if f else list(self._source)
+        return sum(values) / len(values) if values else 0.0
+
+    def aggregate(self, func: Callable[[R, T], R], seed: Optional[R] = None) -> R:
+        it = iter(self._source)
+        if seed is None:
+            acc = next(it)  # type: ignore
+        else:
+            acc = seed
+        for x in it:
+            acc = func(acc, x)
+        return acc
+
+    def any(self, f: Optional[Predicate] = None) -> bool:
+        return any(f(x) if f else x for x in self._source)
+
+    def all(self, f: Predicate) -> bool:
+        return all(f(x) for x in self._source)
+
+    def contains(self, value: T) -> bool:
+        return value in self._source
+
+    def sequence_equal(self, other: Iterable[T]) -> bool:
+        return list(self._source) == list(other)
+
+    def group_by(self, key_f: Callable[[T], K]) -> "Collection[Tuple[K, List[T]]]":
+        sorted_data = sorted(self._source, key=key_f)
+        return Collection([(key, list(group)) for key, group in groupby(sorted_data, key=key_f)])
+
+    def join(
+        self, inner: Iterable[R], outer_key: Callable[[T], K], inner_key: Callable[[R], K], result: Callable[[T, R], R]
+    ) -> "Collection[R]":
+        lookup: Dict[K, List[R]] = {}
+        for i in inner:
+            k = inner_key(i)
+            lookup.setdefault(k, []).append(i)
+        return Collection([result(o, i) for o in self._source for i in lookup.get(outer_key(o), [])])
+
+    def first(self, f: Optional[Predicate] = None) -> T:
+        if f:
+            for x in self._source:
+                if f(x):
+                    return x
+            raise ValueError("No matching element")
+        return next(iter(self._source))
+
+    def first_or_default(self, default: Optional[T] = None) -> Optional[T]:
+        return next(iter(self._source), default)
+
+    def last(self) -> T:
+        return list(self._source)[-1]
+
+    def single(self, f: Optional[Predicate] = None) -> T:
+        items = [x for x in self._source if f(x)] if f else list(self._source)
+        if len(items) != 1:
+            raise ValueError("Sequence does not contain exactly one element")
+        return items[0]
+
+    def to_list(self) -> List[T]:
+        return List(self._source)
+
+    def to_enumerable(self) -> "Enumerable[T]":
+        from cpl.query.enumerable import Enumerable
+
+        return Enumerable(self._source)
+
+    def to_dict(self, key_f: Callable[[T], K], value_f: Selector) -> Dict[K, R]:
+        return {key_f(x): value_f(x) for x in self._source}
+
+    def cast(self, t: Selector) -> "Collection[R]":
+        return Collection([t(x) for x in self._source])
+
+    def of_type(self, t: type) -> "Collection[T]":
+        return Collection([x for x in self._source if isinstance(x, t)])
+
+    def reverse(self) -> "Collection[T]":
+        return Collection(reversed(list(self._source)))
+
+    def zip(self, other: Iterable[R]) -> "Collection[Tuple[T, R]]":
+        return Collection(zip(self._source, other))
+
+    @staticmethod
+    def range(start: int, count: int) -> "Collection[int]":
+        return Collection(range(start, start + count))
+
+    @staticmethod
+    def repeat(value: T, count: int) -> "Collection[T]":
+        return Collection([value for _ in range(count)])
+
+    @staticmethod
+    def empty() -> "Collection[T]":
+        return Collection([])
diff --git a/src/cpl-query/cpl/query/enumerable.py b/src/cpl-query/cpl/query/enumerable.py
new file mode 100644
index 00000000..59df6d98
--- /dev/null
+++ b/src/cpl-query/cpl/query/enumerable.py
@@ -0,0 +1,207 @@
+from itertools import islice, groupby, chain
+from typing import Generic, Callable, Iterable, Iterator, Dict, Tuple, Optional
+
+from cpl.core.typing import T, R
+from cpl.query.typing import Predicate, K, Selector
+
+
+class Enumerable(Generic[T]):
+    def __init__(self, source: Iterable[T]):
+        self._source = source
+
+    def __iter__(self) -> Iterator[T]:
+        return iter(self._source)
+
+    @property
+    def length(self) -> int:
+        return len(list(self._source))
+
+    def where(self, f: Predicate) -> "Enumerable[T]":
+        return Enumerable(x for x in self._source if f(x))
+
+    def select(self, f: Selector) -> "Enumerable[R]":
+        return Enumerable(f(x) for x in self._source)
+
+    def select_many(self, f: Callable[[T], Iterable[R]]) -> "Enumerable[R]":
+        return Enumerable(y for x in self._source for y in f(x))
+
+    def take(self, count: int) -> "Enumerable[T]":
+        return Enumerable(islice(self._source, count))
+
+    def skip(self, count: int) -> "Enumerable[T]":
+        return Enumerable(islice(self._source, count, None))
+
+    def take_while(self, f: Predicate) -> "Enumerable[T]":
+        def generator():
+            for x in self._source:
+                if f(x):
+                    yield x
+                else:
+                    break
+
+        return Enumerable(generator())
+
+    def skip_while(self, f: Predicate) -> "Enumerable[T]":
+        def generator():
+            it = iter(self._source)
+            for x in it:
+                if not f(x):
+                    yield x
+                    break
+            yield from it
+
+        return Enumerable(generator())
+
+    def distinct(self) -> "Enumerable[T]":
+        def generator():
+            seen = set()
+            for x in self._source:
+                if x not in seen:
+                    seen.add(x)
+                    yield x
+
+        return Enumerable(generator())
+
+    def union(self, other: Iterable[T]) -> "Enumerable[T]":
+        return Enumerable(chain(self.distinct(), Enumerable(other).distinct())).distinct()
+
+    def intersect(self, other: Iterable[T]) -> "Enumerable[T]":
+        other_set = set(other)
+        return Enumerable(x for x in self._source if x in other_set)
+
+    def except_(self, other: Iterable[T]) -> "Enumerable[T]":
+        other_set = set(other)
+        return Enumerable(x for x in self._source if x not in other_set)
+
+    def concat(self, other: Iterable[T]) -> "Enumerable[T]":
+        return Enumerable(chain(self._source, other))
+
+    # --- Aggregation ---
+    def count(self) -> int:
+        return sum(1 for _ in self._source)
+
+    def sum(self, f: Optional[Selector] = None) -> R:
+        if f:
+            return sum(f(x) for x in self._source)
+        return sum(self._source)  # type: ignore
+
+    def min(self, f: Optional[Selector] = None) -> R:
+        if f:
+            return min(f(x) for x in self._source)
+        return min(self._source)  # type: ignore
+
+    def max(self, f: Optional[Selector] = None) -> R:
+        if f:
+            return max(f(x) for x in self._source)
+        return max(self._source)  # type: ignore
+
+    def average(self, f: Optional[Callable[[T], float]] = None) -> float:
+        values = list(self.select(f).to_list()) if f else list(self._source)
+        return sum(values) / len(values) if values else 0.0
+
+    def aggregate(self, func: Callable[[R, T], R], seed: Optional[R] = None) -> R:
+        it = iter(self._source)
+        if seed is None:
+            acc = next(it)  # type: ignore
+        else:
+            acc = seed
+        for x in it:
+            acc = func(acc, x)
+        return acc
+
+    def any(self, f: Optional[Predicate] = None) -> bool:
+        return any(f(x) if f else x for x in self._source)
+
+    def all(self, f: Predicate) -> bool:
+        return all(f(x) for x in self._source)
+
+    def contains(self, value: T) -> bool:
+        return any(x == value for x in self._source)
+
+    def sequence_equal(self, other: Iterable[T]) -> bool:
+        return list(self._source) == list(other)
+
+    def group_by(self, key_f: Callable[[T], K]) -> "Enumerable[Tuple[K, List[T]]]":
+        def generator():
+            sorted_data = sorted(self._source, key=key_f)
+            for key, group in groupby(sorted_data, key=key_f):
+                yield (key, list(group))
+
+        return Enumerable(generator())
+
+    def join(
+        self, inner: Iterable[R], outer_key: Callable[[T], K], inner_key: Callable[[R], K], result: Callable[[T, R], R]
+    ) -> "Enumerable[R]":
+        def generator():
+            lookup: Dict[K, List[R]] = {}
+            for i in inner:
+                k = inner_key(i)
+                lookup.setdefault(k, []).append(i)
+            for o in self._source:
+                k = outer_key(o)
+                if k in lookup:
+                    for i in lookup[k]:
+                        yield result(o, i)
+
+        return Enumerable(generator())
+
+    def first(self, f: Optional[Predicate] = None) -> T:
+        if f:
+            for x in self._source:
+                if f(x):
+                    return x
+            raise ValueError("No matching element")
+        return next(iter(self._source))
+
+    def first_or_default(self, default: Optional[T] = None) -> Optional[T]:
+        return next(iter(self._source), default)
+
+    def last(self) -> T:
+        return list(self._source)[-1]
+
+    def single(self, f: Optional[Predicate] = None) -> T:
+        items = [x for x in self._source if f(x)] if f else list(self._source)
+        if len(items) != 1:
+            raise ValueError("Sequence does not contain exactly one element")
+        return items[0]
+
+    def to_list(self) -> "List[T]":
+        from cpl.query.list import List
+        return List(self._source)
+
+    def to_collection(self) -> "Collection[T]":
+        from cpl.query.collection import Collection
+
+        return Collection(self._source)
+
+    def to_set(self) -> "Set[T]":
+        from cpl.query.set import Set
+
+        return Set(self._source)
+
+    def to_dict(self, key_f: Callable[[T], K], value_f: Selector) -> Dict[K, R]:
+        return {key_f(x): value_f(x) for x in self._source}
+
+    def cast(self, t: Selector) -> "Enumerable[R]":
+        return Enumerable(t(x) for x in self._source)
+
+    def of_type(self, t: type) -> "Enumerable[T]":
+        return Enumerable(x for x in self._source if isinstance(x, t))
+
+    def reverse(self) -> "Enumerable[T]":
+        return Enumerable(reversed(list(self._source)))
+
+    def zip(self, other: Iterable[R]) -> "Enumerable[Tuple[T, R]]":
+        return Enumerable(zip(self._source, other))
+
+    @staticmethod
+    def range(start: int, count: int) -> "Enumerable[int]":
+        return Enumerable(range(start, start + count))
+
+    @staticmethod
+    def repeat(value: T, count: int) -> "Enumerable[T]":
+        return Enumerable(value for _ in range(count))
+
+    @staticmethod
+    def empty() -> "Enumerable[T]":
+        return Enumerable([])
diff --git a/src/cpl-query/cpl/query/enumerable/__init__.py b/src/cpl-query/cpl/query/enumerable/__init__.py
deleted file mode 100644
index 75a5d340..00000000
--- a/src/cpl-query/cpl/query/enumerable/__init__.py
+++ /dev/null
@@ -1,2 +0,0 @@
-from .enumerable import Enumerable
-from .enumerable_abc import EnumerableABC
diff --git a/src/cpl-query/cpl/query/enumerable/enumerable.py b/src/cpl-query/cpl/query/enumerable/enumerable.py
deleted file mode 100644
index f1e795ef..00000000
--- a/src/cpl-query/cpl/query/enumerable/enumerable.py
+++ /dev/null
@@ -1,12 +0,0 @@
-from cpl.query.enumerable.enumerable_abc import EnumerableABC
-
-
-def _default_lambda(x: object):
-    return x
-
-
-class Enumerable(EnumerableABC):
-    r"""Implementation of :class: `cpl.query.enumerable.enumerable_abc.EnumerableABC`"""
-
-    def __init__(self, t: type = None, values: list = None):
-        EnumerableABC.__init__(self, t, values)
diff --git a/src/cpl-query/cpl/query/enumerable/enumerable_abc.py b/src/cpl-query/cpl/query/enumerable/enumerable_abc.py
deleted file mode 100644
index 33410ba2..00000000
--- a/src/cpl-query/cpl/query/enumerable/enumerable_abc.py
+++ /dev/null
@@ -1,21 +0,0 @@
-from abc import abstractmethod
-
-from cpl.query.base.queryable_abc import QueryableABC
-
-
-class EnumerableABC(QueryableABC):
-    r"""ABC to define functions on list"""
-
-    @abstractmethod
-    def __init__(self, t: type = None, values: list = None):
-        QueryableABC.__init__(self, t, values)
-
-    def to_iterable(self) -> "IterableABC":
-        r"""Converts :class: `cpl.query.enumerable.enumerable_abc.EnumerableABC` to :class: `cpl.query.iterable.iterable_abc.IterableABC`
-
-        Returns:
-            :class: `cpl.query.iterable.iterable_abc.IterableABC`
-        """
-        from cpl.query.iterable.iterable import Iterable
-
-        return Iterable(self._type, self.to_list())
diff --git a/src/cpl-query/cpl/query/exceptions.py b/src/cpl-query/cpl/query/exceptions.py
deleted file mode 100644
index 5081dd06..00000000
--- a/src/cpl-query/cpl/query/exceptions.py
+++ /dev/null
@@ -1,33 +0,0 @@
-from enum import Enum
-
-
-# models
-class ExceptionArgument(Enum):
-    list = "list"
-    func = "func"
-    type = "type"
-    value = "value"
-    index = "index"
-
-
-# exceptions
-class ArgumentNoneException(Exception):
-    r"""Exception when argument is None"""
-
-    def __init__(self, arg: ExceptionArgument):
-        Exception.__init__(self, f"argument {arg} is None")
-
-
-class IndexOutOfRangeException(Exception):
-    r"""Exception when index is out of range"""
-
-    def __init__(self, err: str = None):
-        Exception.__init__(self, f"List index out of range" if err is None else err)
-
-
-class InvalidTypeException(Exception):
-    r"""Exception when type is invalid"""
-
-
-class WrongTypeException(Exception):
-    r"""Exception when type is unexpected"""
diff --git a/src/cpl-query/cpl/query/extension/__init__.py b/src/cpl-query/cpl/query/extension/__init__.py
deleted file mode 100644
index 9ef128d3..00000000
--- a/src/cpl-query/cpl/query/extension/__init__.py
+++ /dev/null
@@ -1 +0,0 @@
-from .list import List
diff --git a/src/cpl-query/cpl/query/extension/list.py b/src/cpl-query/cpl/query/extension/list.py
deleted file mode 100644
index d2202831..00000000
--- a/src/cpl-query/cpl/query/extension/list.py
+++ /dev/null
@@ -1,36 +0,0 @@
-from cpl.query.enumerable.enumerable_abc import EnumerableABC
-from cpl.query.iterable.iterable import Iterable
-
-
-class List(Iterable):
-    r"""Implementation of :class: `cpl.query.extension.iterable.Iterable`"""
-
-    def __init__(self, t: type = None, values: Iterable = None):
-        Iterable.__init__(self, t, values)
-
-    def __getitem__(self, *args):
-        return self._values.__getitem__(*args)
-
-    def __setitem__(self, *args):
-        self._values.__setitem__(*args)
-
-    def __delitem__(self, *args):
-        self._values.__delitem__(*args)
-
-    def to_enumerable(self) -> EnumerableABC:
-        r"""Converts :class: `cpl.query.iterable.iterable_abc.IterableABC` to :class: `cpl.query.enumerable.enumerable_abc.EnumerableABC`
-
-        Returns:
-            :class: `cpl.query.enumerable.enumerable_abc.EnumerableABC`
-        """
-        from cpl.query.enumerable.enumerable import Enumerable
-
-        return Enumerable(self._type, self.to_list())
-
-    def to_iterable(self) -> Iterable:
-        r"""Converts :class: `cpl.query.enumerable.enumerable_abc.EnumerableABC` to :class: `cpl.query.iterable.iterable_abc.IterableABC`
-
-        Returns:
-            :class: `cpl.query.iterable.iterable_abc.IterableABC`
-        """
-        return Iterable(self._type, self.to_list())
diff --git a/src/cpl-query/cpl/query/immutable_list.py b/src/cpl-query/cpl/query/immutable_list.py
new file mode 100644
index 00000000..0c3d0486
--- /dev/null
+++ b/src/cpl-query/cpl/query/immutable_list.py
@@ -0,0 +1,45 @@
+from typing import Generic, Iterable, Iterator, Optional
+
+from cpl.core.typing import T
+from cpl.query.enumerable import Enumerable
+
+
+class ImmutableList(Generic[T], Enumerable[T]):
+    def __init__(self, source: Optional[Iterable[T]] = None):
+        if source is None:
+            source = []
+
+        Enumerable.__init__(self, source)
+
+    @property
+    def _items(self) -> list[T]:
+        return list(self._source)
+
+    def __iter__(self) -> Iterator[T]:
+        return iter(self._items)
+
+    def __len__(self) -> int:
+        return len(self._items)
+
+    def __getitem__(self, index: int) -> T:
+        return self._items[index]
+
+    def __contains__(self, item: T) -> bool:
+        return item in self._items
+
+    def __repr__(self) -> str:
+        return f"List({self._items!r})"
+
+    @property
+    def length(self) -> int:
+        return len(self._items)
+
+    def to_enumerable(self) -> "Enumerable[T]":
+        from cpl.query.enumerable import Enumerable
+
+        return Enumerable(self._items)
+
+    def to_collection(self) -> "Collection[T]":
+        from cpl.query.collection import Collection
+
+        return Collection(self._items)
diff --git a/src/cpl-query/cpl/query/immutable_set.py b/src/cpl-query/cpl/query/immutable_set.py
new file mode 100644
index 00000000..ce28fc0f
--- /dev/null
+++ b/src/cpl-query/cpl/query/immutable_set.py
@@ -0,0 +1,44 @@
+from typing import Generic, Iterable, Iterator, Optional
+
+from cpl.core.typing import T
+from cpl.query.enumerable import Enumerable
+
+
+class ImmutableSet(Generic[T], Enumerable[T]):
+    def __init__(self, source: Optional[Iterable[T]] = None):
+        if source is None:
+            source = set()
+
+        self.__source = source
+        Enumerable.__init__(self, [])
+
+    @property
+    def _source(self) -> set[T]:
+        return self.__source
+
+    @_source.setter
+    def _source(self, value: set[T]) -> None:
+        if not isinstance(value, set):
+            value = set(value)
+
+        self.__source = value
+
+    def __iter__(self) -> Iterator[T]:
+        return iter(self._source)
+
+    def __len__(self) -> int:
+        return len(self._source)
+
+    def __contains__(self, item: T) -> bool:
+        return item in self._source
+
+    def __repr__(self) -> str:
+        return f"Set({self._source!r})"
+
+    @property
+    def length(self) -> int:
+        return len(self._source)
+
+    def to_enumerable(self) -> "Enumerable[T]":
+        from cpl.query.enumerable import Enumerable
+        return Enumerable(self._source)
\ No newline at end of file
diff --git a/src/cpl-query/cpl/query/iterable/__init__.py b/src/cpl-query/cpl/query/iterable/__init__.py
deleted file mode 100644
index 07f325d4..00000000
--- a/src/cpl-query/cpl/query/iterable/__init__.py
+++ /dev/null
@@ -1,2 +0,0 @@
-from .iterable_abc import IterableABC
-from .iterable import Iterable
diff --git a/src/cpl-query/cpl/query/iterable/iterable.py b/src/cpl-query/cpl/query/iterable/iterable.py
deleted file mode 100644
index 3a3292af..00000000
--- a/src/cpl-query/cpl/query/iterable/iterable.py
+++ /dev/null
@@ -1,8 +0,0 @@
-from typing import Iterable as TIterable
-
-from cpl.query.iterable.iterable_abc import IterableABC
-
-
-class Iterable(IterableABC):
-    def __init__(self, t: type = None, values: TIterable = None):
-        IterableABC.__init__(self, t, values)
diff --git a/src/cpl-query/cpl/query/iterable/iterable_abc.py b/src/cpl-query/cpl/query/iterable/iterable_abc.py
deleted file mode 100644
index d2316fdf..00000000
--- a/src/cpl-query/cpl/query/iterable/iterable_abc.py
+++ /dev/null
@@ -1,71 +0,0 @@
-from abc import abstractmethod
-from typing import Iterable
-
-from cpl.query.base.queryable_abc import QueryableABC
-
-
-class IterableABC(QueryableABC):
-    r"""ABC to define functions on list"""
-
-    @abstractmethod
-    def __init__(self, t: type = None, values: Iterable = None):
-        QueryableABC.__init__(self, t, values)
-
-    def __str__(self):
-        return str(self.to_list())
-
-    def append(self, _object: object):
-        self.add(_object)
-
-    def add(self, _object: object):
-        r"""Adds element to list
-
-        Parameter:
-            _object: :class:`object`
-                value
-        """
-        self._check_type(_object)
-        self._values.append(_object)
-
-    def extend(self, __iterable: Iterable) -> "IterableABC":
-        r"""Adds elements of given list to list
-
-        Parameter:
-            __iterable: :class: `cpl.query.extension.iterable.Iterable`
-                index
-        """
-        for value in __iterable:
-            self.append(value)
-
-        return self
-
-    def remove(self, _object: object):
-        r"""Removes element from list
-
-        Parameter:
-            _object: :class:`object`
-                value
-        """
-        if _object not in self:
-            raise ValueError
-
-        self._values.remove(_object)
-
-    def remove_at(self, _index: int):
-        r"""Removes element from list
-
-        Parameter:
-            _object: :class:`object`
-                value
-        """
-        self._values.pop(_index)
-
-    def to_enumerable(self) -> "EnumerableABC":
-        r"""Converts :class: `cpl.query.iterable.iterable_abc.IterableABC` to :class: `cpl.query.enumerable.enumerable_abc.EnumerableABC`
-
-        Returns:
-            :class: `cpl.query.enumerable.enumerable_abc.EnumerableABC`
-        """
-        from cpl.query.enumerable.enumerable import Enumerable
-
-        return Enumerable(self._type, self.to_list())
diff --git a/src/cpl-query/cpl/query/list.py b/src/cpl-query/cpl/query/list.py
new file mode 100644
index 00000000..1ec00a72
--- /dev/null
+++ b/src/cpl-query/cpl/query/list.py
@@ -0,0 +1,66 @@
+from typing import Generic, Iterable, Iterator, Optional
+
+from cpl.core.typing import T
+from cpl.query.enumerable import Enumerable
+
+
+class List(Generic[T], Enumerable[T]):
+    def __init__(self, source: Optional[Iterable[T]] = None):
+        if source is None:
+            source = []
+
+        Enumerable.__init__(self, source)
+
+    @property
+    def _items(self) -> list[T]:
+        return list(self._source)
+
+    def __iter__(self) -> Iterator[T]:
+        return iter(self._items)
+
+    def __len__(self) -> int:
+        return len(self._items)
+
+    def __getitem__(self, index: int) -> T:
+        return self._items[index]
+
+    def __setitem__(self, index: int, value: T) -> None:
+        self._items[index] = value
+
+    def __contains__(self, item: T) -> bool:
+        return item in self._items
+
+    def __repr__(self) -> str:
+        return f"List({self._items!r})"
+
+    @property
+    def length(self) -> int:
+        return len(self._items)
+
+    def add(self, item: T) -> None:
+        self._items.append(item)
+
+    def extend(self, items: Iterable[T]) -> None:
+        self._items.extend(items)
+
+    def insert(self, index: int, item: T) -> None:
+        self._items.insert(index, item)
+
+    def remove(self, item: T) -> None:
+        self._items.remove(item)
+
+    def pop(self, index: int = -1) -> T:
+        return self._items.pop(index)
+
+    def clear(self) -> None:
+        self._items.clear()
+
+    def to_enumerable(self) -> "Enumerable[T]":
+        from cpl.query.enumerable import Enumerable
+
+        return Enumerable(self._items)
+
+    def to_collection(self) -> "Collection[T]":
+        from cpl.query.collection import Collection
+
+        return Collection(self._items)
diff --git a/src/cpl-query/cpl/query/protocol/__init__.py b/src/cpl-query/cpl/query/protocol/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/src/cpl-query/cpl/query/protocol/sequence.py b/src/cpl-query/cpl/query/protocol/sequence.py
new file mode 100644
index 00000000..73da8423
--- /dev/null
+++ b/src/cpl-query/cpl/query/protocol/sequence.py
@@ -0,0 +1,59 @@
+from typing import Protocol, Callable, Dict, Tuple, Optional, Iterable
+
+from cpl.core.typing import T, R
+from cpl.query.list import List
+from cpl.query.typing import Selector, Predicate, K
+
+
+class Sequence(Protocol[T]):
+    def select(self, f: Selector) -> "Sequence[R]": ...
+    def where(self, f: Predicate) -> "Sequence[T]": ...
+    def select_many(self, f: Callable[[T], Iterable[R]]) -> "Sequence[R]": ...
+
+    def take(self, count: int) -> "Sequence[T]": ...
+    def skip(self, count: int) -> "Sequence[T]": ...
+    def take_while(self, f: Predicate) -> "Sequence[T]": ...
+    def skip_while(self, f: Predicate) -> "Sequence[T]": ...
+
+    def distinct(self) -> "Sequence[T]": ...
+    def union(self, other: Iterable[T]) -> "Sequence[T]": ...
+    def intersect(self, other: Iterable[T]) -> "Sequence[T]": ...
+    def except_(self, other: Iterable[T]) -> "Sequence[T]": ...
+    def concat(self, other: Iterable[T]) -> "Sequence[T]": ...
+
+    def count(self) -> int: ...
+    def sum(self, f: Optional[Selector] = None) -> R: ...
+    def min(self, f: Optional[Selector] = None) -> R: ...
+    def max(self, f: Optional[Selector] = None) -> R: ...
+    def average(self, f: Optional[Callable[[T], float]] = None) -> float: ...
+    def aggregate(self, func: Callable[[R, T], R], seed: Optional[R] = None) -> R: ...
+
+    def any(self, f: Optional[Predicate] = None) -> bool: ...
+    def all(self, f: Predicate) -> bool: ...
+    def contains(self, value: T) -> bool: ...
+    def sequence_equal(self, other: Iterable[T]) -> bool: ...
+
+    def group_by(self, key_f: Callable[[T], K]) -> "Sequence[Tuple[K, List[T]]]": ...
+    def join(
+        self, inner: Iterable[R], outer_key: Callable[[T], K], inner_key: Callable[[R], K], result: Callable[[T, R], R]
+    ) -> "Sequence[R]": ...
+
+    def first(self, f: Optional[Predicate] = None) -> T: ...
+    def first_or_default(self, default: Optional[T] = None) -> Optional[T]: ...
+    def last(self) -> T: ...
+    def single(self, f: Optional[Predicate] = None) -> T: ...
+
+    def to_list(self) -> List[T]: ...
+    def to_dict(self, key_f: Callable[[T], K], value_f: Selector) -> Dict[K, R]: ...
+
+    def cast(self, t: Selector) -> "Sequence[R]": ...
+    def of_type(self, t: type) -> "Sequence[T]": ...
+    def reverse(self) -> "Sequence[T]": ...
+    def zip(self, other: Iterable[R]) -> "Sequence[Tuple[T, R]]": ...
+
+    @staticmethod
+    def range(start: int, count: int) -> "Sequence[int]": ...
+    @staticmethod
+    def repeat(value: T, count: int) -> "Sequence[T]": ...
+    @staticmethod
+    def empty() -> "Sequence[T]": ...
diff --git a/src/cpl-query/cpl/query/set.py b/src/cpl-query/cpl/query/set.py
new file mode 100644
index 00000000..82e40a52
--- /dev/null
+++ b/src/cpl-query/cpl/query/set.py
@@ -0,0 +1,53 @@
+from typing import Generic, Iterable, Iterator, Optional
+
+from cpl.core.typing import T
+from cpl.query.enumerable import Enumerable
+
+
+class Set(Generic[T], Enumerable[T]):
+    def __init__(self, source: Optional[Iterable[T]] = None):
+        if source is None:
+            source = set()
+
+        self.__source = source
+        Enumerable.__init__(self, [])
+
+    @property
+    def _source(self) -> set[T]:
+        return self.__source
+
+    @_source.setter
+    def _source(self, value: set[T]) -> None:
+        if not isinstance(value, set):
+            value = set(value)
+
+        self.__source = value
+
+    def __iter__(self) -> Iterator[T]:
+        return iter(self._source)
+
+    def __len__(self) -> int:
+        return len(self._source)
+
+    def __contains__(self, item: T) -> bool:
+        return item in self._source
+
+    def __repr__(self) -> str:
+        return f"Set({self._source!r})"
+
+    @property
+    def length(self) -> int:
+        return len(self._source)
+
+    def add(self, item: T) -> None:
+        self._source.add(item)
+
+    def remove(self, item: T) -> None:
+        self._source.remove(item)
+
+    def clear(self) -> None:
+        self._source.clear()
+
+    def to_enumerable(self) -> "Enumerable[T]":
+        from cpl.query.enumerable import Enumerable
+        return Enumerable(self._source)
\ No newline at end of file
diff --git a/src/cpl-query/cpl/query/typing.py b/src/cpl-query/cpl/query/typing.py
new file mode 100644
index 00000000..b7297329
--- /dev/null
+++ b/src/cpl-query/cpl/query/typing.py
@@ -0,0 +1,8 @@
+from typing import Callable, TypeVar
+
+from cpl.core.typing import T, R
+
+K = TypeVar("K")
+
+Predicate = Callable[[T], bool]
+Selector = Callable[[T], R]
diff --git a/unittests/unittests_query/iterable_query_test_case.py b/unittests/unittests_query/iterable_query_test_case.py
index fccf9468..eda2a948 100644
--- a/unittests/unittests_query/iterable_query_test_case.py
+++ b/unittests/unittests_query/iterable_query_test_case.py
@@ -5,7 +5,7 @@ from random import randint
 from cpl.core.utils import String
 from cpl.query.exceptions import InvalidTypeException, ArgumentNoneException
 from cpl.query.extension.list import List
-from cpl.query.iterable import Iterable
+from cpl.query.collection import Iterable
 from unittests_query.models import User, Address
 
 
diff --git a/unittests/unittests_query/performance_test_case.py b/unittests/unittests_query/performance_test_case.py
index b8f52a3a..305e7015 100644
--- a/unittests/unittests_query/performance_test_case.py
+++ b/unittests/unittests_query/performance_test_case.py
@@ -3,7 +3,7 @@ import timeit
 import unittest
 
 from cpl.query.enumerable import Enumerable
-from cpl.query.iterable import Iterable
+from cpl.query.collection import Iterable
 
 VALUES = 10000
 COUNT = 50
diff --git a/unittests/unittests_query/sequence_test_case.py b/unittests/unittests_query/sequence_test_case.py
index f922497c..134e9900 100644
--- a/unittests/unittests_query/sequence_test_case.py
+++ b/unittests/unittests_query/sequence_test_case.py
@@ -2,7 +2,7 @@ import unittest
 
 from cpl.query.enumerable import Enumerable
 from cpl.query.extension.list import List
-from cpl.query.iterable import Iterable
+from cpl.query.collection import Iterable
 
 
 class SequenceTestCase(unittest.TestCase):