diff --git a/src/multi_install/abc/application_service_abc.py b/src/multi_install/abc/application_service_abc.py
new file mode 100644
index 0000000..6f407ff
--- /dev/null
+++ b/src/multi_install/abc/application_service_abc.py
@@ -0,0 +1,7 @@
+from abc import ABC, abstractmethod
+
+
+class ApplicationServiceABC(ABC):
+
+    @abstractmethod
+    def __init__(self): pass
diff --git a/src/multi_install/abc/collection_service_abc.py b/src/multi_install/abc/collection_service_abc.py
new file mode 100644
index 0000000..a6d7c57
--- /dev/null
+++ b/src/multi_install/abc/collection_service_abc.py
@@ -0,0 +1,7 @@
+from abc import ABC, abstractmethod
+
+
+class CollectionServiceABC(ABC):
+
+    @abstractmethod
+    def __init__(self): pass
diff --git a/src/multi_install/model/__init__.py b/src/multi_install/model/__init__.py
new file mode 100644
index 0000000..425ab6c
--- /dev/null
+++ b/src/multi_install/model/__init__.py
@@ -0,0 +1 @@
+# imports
diff --git a/src/multi_install/service/application_service.py b/src/multi_install/service/application_service.py
new file mode 100644
index 0000000..4946dbd
--- /dev/null
+++ b/src/multi_install/service/application_service.py
@@ -0,0 +1,4 @@
+class ApplicationService:
+
+    def __init__(self):
+        pass
diff --git a/src/multi_install/service/collection_service.py b/src/multi_install/service/collection_service.py
new file mode 100644
index 0000000..423fe22
--- /dev/null
+++ b/src/multi_install/service/collection_service.py
@@ -0,0 +1,4 @@
+class CollectionService:
+
+    def __init__(self):
+        pass
diff --git a/src/multi_install/service/menu_service.py b/src/multi_install/service/menu_service.py
index f94a636..e50d9db 100644
--- a/src/multi_install/service/menu_service.py
+++ b/src/multi_install/service/menu_service.py
@@ -4,6 +4,7 @@ from cpl_core.console import Console
 from cpl_query.extension import List
 from multi_install.abc.menu_service_abc import MenuServiceABC
 from multi_install.config.os_settings import OSSettings
+from multi_install.model.main_menu_enum import MainMenuEnum
 
 
 class MenuService(MenuServiceABC):
@@ -16,53 +17,75 @@ class MenuService(MenuServiceABC):
     def run(self):
         is_end = False
         while not is_end:
-            self.select_os()
-            main_menu = self.main_menu()
-            
-            if main_menu == 'Exit':
-                is_end = True
+            is_end = self.select_os()
+            if not is_end:
+                is_end = self.main_menu()
                 
-            elif main_menu == 'Back':
-                break
+            if is_end:
+                Console.write_line()
         
-    def select_os(self):
+    def select_os(self) -> bool:
         Console.clear()
         options = List(str, self._os_settings.operating_systems.copy())
         options.append('Exit')
         Console.write_line('Select option:')
-        options.for_each(lambda o: Console.write_line(f'[{options.index(o)}] {o}'))
-        os = int(Console.read('\n:'))
+        options.for_each(lambda o: Console.write_line(f'[{options.index(o)+1}] {o}'))
+        os = 0
+        try:
+            os = int(Console.read('\n:'))-1
+        except ValueError:
+            Console.error('Input value must be int!')
+            return True
+        
         if os == options.index('Exit'):
-            exit()
+            return True
         
         self._os = os
-    
-    def main_menu(self) -> str:
+        return False
+        
+    def main_menu(self) -> bool:
         Console.clear()
         options = List(str, [
-            'Install collection',
-            'Uninstall collection',
-            'Add collection',
-            'Remove collection',
+            MainMenuEnum.install_collection.value,
+            MainMenuEnum.uninstall_collection.value,
+            MainMenuEnum.add_collection.value,
+            MainMenuEnum.remove_collection.value,
             
-            'Install application',
-            'Uninstall application',
-            'Add application',
-            'Remove application',
-            'Add application',
+            MainMenuEnum.install_application.value,
+            MainMenuEnum.uninstall_application.value,
+            MainMenuEnum.add_application.value,
+            MainMenuEnum.remove_application.value,
             
-            'Back',
-            'Exit'
+            MainMenuEnum.back.value,
+            MainMenuEnum.exit.value
         ])
         Console.write_line('Select option:')
-        options.for_each(lambda o: Console.write_line(f'[{options.index(o)}] {o}'))
-        selected = int(Console.read('\n:'))
-        if selected == options.index('Exit'):
-            exit()
+        options.for_each(lambda o: Console.write_line(f'[{options.index(o)+1}] {o}'))
+        selected = 0
+        try:
+            selected = int(Console.read('\n:'))-1
+        except ValueError:
+            Console.error('Input value must be int!')
+            return True
         
-        return selected
-    
-    def select_collection(self) -> str: 
-        options = []
-        options.append('Exit')
-        return Console.select('>', 'Select collection:', options)
+        # collection menu
+        if selected == options.index(MainMenuEnum.install_collection.value): pass
+        elif selected == options.index(MainMenuEnum.uninstall_collection.value): pass
+        elif selected == options.index(MainMenuEnum.add_collection.value): pass
+        elif selected == options.index(MainMenuEnum.remove_collection.value): pass
+        
+        # application menu
+        elif selected == options.index(MainMenuEnum.install_application.value): pass
+        elif selected == options.index(MainMenuEnum.uninstall_application.value): pass
+        elif selected == options.index(MainMenuEnum.add_application.value): pass
+        elif selected == options.index(MainMenuEnum.remove_application.value): pass
+        
+        elif selected == options.index(MainMenuEnum.back.value):
+            return
+        elif selected == options.index(MainMenuEnum.exit.value):
+            return True
+            
+        else:
+            raise Exception(f'Unknown option: {selected}')
+        
+        return False