diff --git a/Demo/Data/LocalData/Entity/Group.cs b/Demo/Data/LocalData/Entity/Group.cs
index 6041311..572faae 100644
--- a/Demo/Data/LocalData/Entity/Group.cs
+++ b/Demo/Data/LocalData/Entity/Group.cs
@@ -4,7 +4,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace Demo.domain.Models
+namespace Demo.Domain.Models
 {
     public class GroupLocalEntity
     {
diff --git a/Demo/Data/LocalData/Entity/Presence.cs b/Demo/Data/LocalData/Entity/Presence.cs
index 70b8d1e..79cbb6a 100644
--- a/Demo/Data/LocalData/Entity/Presence.cs
+++ b/Demo/Data/LocalData/Entity/Presence.cs
@@ -4,7 +4,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace Demo.domain.Models
+namespace Demo.Domain.Models
 {
     internal class PresenceLocalEntity
     {
diff --git a/Demo/Data/LocalData/Entity/User.cs b/Demo/Data/LocalData/Entity/User.cs
index 5af4881..6415232 100644
--- a/Demo/Data/LocalData/Entity/User.cs
+++ b/Demo/Data/LocalData/Entity/User.cs
@@ -4,7 +4,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace Demo.domain.Models
+namespace Demo.Domain.Models
 {
     public class UserLocalEnity : IEquatable<UserLocalEnity>
     {
diff --git a/Demo/Data/LocalData/LocalStaticData.cs b/Demo/Data/LocalData/LocalStaticData.cs
index 50e54f7..058fc25 100644
--- a/Demo/Data/LocalData/LocalStaticData.cs
+++ b/Demo/Data/LocalData/LocalStaticData.cs
@@ -1,4 +1,4 @@
-using Demo.domain.Models;
+using Demo.Domain.Models;
 using System;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/Demo/Data/Repository/GroupRepositoryImpl.cs b/Demo/Data/Repository/GroupRepositoryImpl.cs
index e5b9a29..a21ae9f 100644
--- a/Demo/Data/Repository/GroupRepositoryImpl.cs
+++ b/Demo/Data/Repository/GroupRepositoryImpl.cs
@@ -1,5 +1,5 @@
 using Demo.Data.LocalData;
-using Demo.domain.Models;
+using Demo.Domain.Models;
 using System;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/Demo/Data/Repository/UserRepositoryImpl.cs b/Demo/Data/Repository/UserRepositoryImpl.cs
index bf9ae8c..48adfb2 100644
--- a/Demo/Data/Repository/UserRepositoryImpl.cs
+++ b/Demo/Data/Repository/UserRepositoryImpl.cs
@@ -1,5 +1,5 @@
 using Demo.Data.LocalData;
-using Demo.domain.Models;
+using Demo.Domain.Models;
 using System;
 using System.Collections.Generic;
 using System.Linq;
diff --git a/Demo/Domain/Models/Group.cs b/Demo/Domain/Models/Group.cs
index ce0914b..90e02ff 100644
--- a/Demo/Domain/Models/Group.cs
+++ b/Demo/Domain/Models/Group.cs
@@ -4,7 +4,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace Demo.domain.Models
+namespace Demo.Domain.Models
 {
     public class Group
     {
diff --git a/Demo/Domain/Models/Presence.cs b/Demo/Domain/Models/Presence.cs
index a5fe7a0..127cc34 100644
--- a/Demo/Domain/Models/Presence.cs
+++ b/Demo/Domain/Models/Presence.cs
@@ -4,7 +4,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace Demo.domain.Models
+namespace Demo.Domain.Models
 {
     public class Presence
     {
diff --git a/Demo/Domain/Models/User.cs b/Demo/Domain/Models/User.cs
index cffca41..c0fef3a 100644
--- a/Demo/Domain/Models/User.cs
+++ b/Demo/Domain/Models/User.cs
@@ -4,7 +4,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace Demo.domain.Models
+namespace Demo.Domain.Models
 {
     public class User
     {
diff --git a/Demo/Domain/UseCase/GroupUseCase.cs b/Demo/Domain/UseCase/GroupUseCase.cs
new file mode 100644
index 0000000..a572fea
--- /dev/null
+++ b/Demo/Domain/UseCase/GroupUseCase.cs
@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Demo.Domain.Models;
+
+namespace Demo.Domain.UseCase
+{
+
+
+
+    public class GroupUseCase
+    {
+        private List<Group> _groups = new List<Group>();
+        private int _nextId;
+
+        public IEnumerable<Group> GetAllGroups() => _groups;
+
+        public void AddGroup(string name)
+        {
+            _groups.Add(new Group { Id = _nextId++, Name = name });
+        }
+
+        public void UpdateGroupName(Guid id, string newName, bool Id)
+        {
+            var group = _groups.FirstOrDefault(g => Id);
+            if (group != null)
+                group.Name = newName;
+        }
+    }
+
+}
diff --git a/Demo/Domain/UseCase/UserUseCase.cs b/Demo/Domain/UseCase/UserUseCase.cs
index f1f44e1..08b7e40 100644
--- a/Demo/Domain/UseCase/UserUseCase.cs
+++ b/Demo/Domain/UseCase/UserUseCase.cs
@@ -1,46 +1,44 @@
 using Demo.Data.Repository;
-using Demo.domain.Models;
+using Demo.Domain.Models;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace Demo.Domain.UseCase
+
+public class UserUseCase
 {
-    public class UserUseCase
+    private List<User> _users = new List<User>();
+    private UserRepositoryImpl userRepositoryImpl;
+    private GroupRepositoryImpl groupRepositoryImpl;
+
+    public UserUseCase(UserRepositoryImpl userRepositoryImpl, GroupRepositoryImpl groupRepositoryImpl)
     {
-        private UserRepositoryImpl _repositoryUserImpl;
-        private GroupRepositoryImpl _repositoryGroupImpl;
+        this.userRepositoryImpl = userRepositoryImpl;
+        this.groupRepositoryImpl = groupRepositoryImpl;
+    }
 
-        public UserUseCase(UserRepositoryImpl repositoryImpl, GroupRepositoryImpl repositoryGroupImpl)
-        {
-            _repositoryUserImpl = repositoryImpl;
-            _repositoryGroupImpl = repositoryGroupImpl;
-        }
+    public IEnumerable<User> GetAllUsers() => _users;
 
-      public List<Group> GetAllGroups() => _repositoryGroupImpl.GetAllGroups()
-            .Select(it => new Group { Id  = it.Id, Name = it.Name}).ToList();
-      public List<User> GetAllUsers() => _repositoryUserImpl.GetAllUsers
-            .Join(_repositoryGroupImpl.GetAllGroups(),
-            user => user.GroupID,
-            group => group.Id,
-            (user, group) => 
-            new User { FIO = user.FIO, 
-                Guid = user.Guid, 
-                Group = new Group {Id = group.Id, Name = group.Name } }
-          ).ToList();
+    public User FindUserByGuid(Guid id) => _users.FirstOrDefault(u => u. Guid == id);
 
-        public bool RemoveUserByGuid(Guid userGuid) {
-           return _repositoryUserImpl.RemoveUserByGuid(userGuid);
-        }
-        public User UpdateUser(User user) {
-            UserLocalEnity userLocalEnity = new UserLocalEnity { FIO = user.FIO, GroupID = user.Group.Id, Guid = user.Guid };
-            UserLocalEnity? result = _repositoryUserImpl.UpdateUser(userLocalEnity);
-            if (result == null) throw new Exception("");
-            Group? group = GetAllGroups().FirstOrDefault(it => it.Id == result!.GroupID);
-            if (group == null) throw new Exception("");
-            return new User { FIO = user.FIO, Guid = user.Guid,  Group = group};
-        }
+    public void DeleteUserByGuid(Guid id)
+    {
+        var user = _users.FirstOrDefault(u => u.Guid == id);
+        if (user != null)
+            _users.Remove(user);
+    }
+
+    public void UpdateUserByGuid(Guid id, string newName)
+    {
+        var user = _users.FirstOrDefault(u => u.Guid == id);
+        if (user != null)
+            user.FIO = newName;
+    }
+
+    internal bool RemoveUserByGuid(Guid guidUser)
+    {
+        throw new NotImplementedException();
     }
 }
diff --git a/Demo/Program.cs b/Demo/Program.cs
index 9ebb621..c3ff9b0 100644
--- a/Demo/Program.cs
+++ b/Demo/Program.cs
@@ -1,6 +1,5 @@
 
 using Demo.Data.Repository;
-using Demo.Domain.UseCase;
 using Demo.UI;
 
 GroupRepositoryImpl groupRepositoryImpl = new GroupRepositoryImpl();
diff --git a/Demo/UI/MainMenu.cs b/Demo/UI/MainMenu.cs
index ce13884..d886091 100644
--- a/Demo/UI/MainMenu.cs
+++ b/Demo/UI/MainMenu.cs
@@ -1,11 +1,4 @@
-using Demo.Domain.UseCase;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace Demo.UI
+namespace Demo.UI
 {
     public class MainMenuUI
     {
diff --git a/Demo/UI/UserConsole.cs b/Demo/UI/UserConsole.cs
index 15ec296..605db10 100644
--- a/Demo/UI/UserConsole.cs
+++ b/Demo/UI/UserConsole.cs
@@ -1,9 +1,4 @@
-using Demo.Domain.UseCase;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System.Text;
 
 namespace Demo.UI
 {