diff --git a/csharp/App/Backend/Controllers/Controller.cs b/csharp/App/Backend/Controllers/Controller.cs
index 322242871..2cb2ba46f 100644
--- a/csharp/App/Backend/Controllers/Controller.cs
+++ b/csharp/App/Backend/Controllers/Controller.cs
@@ -4,7 +4,6 @@ using InnovEnergy.App.Backend.DataTypes.Methods;
 using InnovEnergy.App.Backend.Relations;
 using Microsoft.AspNetCore.Mvc;
 using static System.Net.HttpStatusCode;
-using static System.String;
 using Folder = InnovEnergy.App.Backend.DataTypes.Folder;
 using Installation = InnovEnergy.App.Backend.DataTypes.Installation;
 using Object = System.Object;
diff --git a/csharp/App/Backend/DataTypes/Methods/Folder.cs b/csharp/App/Backend/DataTypes/Methods/Folder.cs
index 274574a4f..321aca9eb 100644
--- a/csharp/App/Backend/DataTypes/Methods/Folder.cs
+++ b/csharp/App/Backend/DataTypes/Methods/Folder.cs
@@ -33,7 +33,9 @@ public static class FolderMethods
 
     public static IEnumerable<Folder> Ancestors(this Folder folder)
     {
-        return folder.Unfold(Parent);
+        return folder
+              .Unfold(Parent)
+              .Skip(1);  // skip self
     }
 
     public static Folder? Parent(this Folder folder)
diff --git a/csharp/App/Backend/DataTypes/Methods/Installation.cs b/csharp/App/Backend/DataTypes/Methods/Installation.cs
index 15fda5ff1..6d50415fc 100644
--- a/csharp/App/Backend/DataTypes/Methods/Installation.cs
+++ b/csharp/App/Backend/DataTypes/Methods/Installation.cs
@@ -33,9 +33,12 @@ public static class InstallationMethods
     {
         var parentFolder = Parent(installation);
 
-        return parentFolder is null 
-             ? Enumerable.Empty<Folder>() 
-             : parentFolder.Ancestors();
+        if (parentFolder is null)
+            return Enumerable.Empty<Folder>();
+        
+        return parentFolder
+              .Ancestors()
+              .Prepend(parentFolder);
     }
     
     public static Folder? Parent(this Installation installation)
diff --git a/csharp/App/Backend/DataTypes/Methods/Session.cs b/csharp/App/Backend/DataTypes/Methods/Session.cs
index fc66f90d1..86960dab2 100644
--- a/csharp/App/Backend/DataTypes/Methods/Session.cs
+++ b/csharp/App/Backend/DataTypes/Methods/Session.cs
@@ -110,6 +110,34 @@ public static class SessionMethods
             && Db.Delete(userToDelete);
     }
 
+    
+    public static Boolean GrantUserAccessTo(this Session? session, User? user, Installation? installation)
+    {
+        var sessionUser = session?.User;
+
+        return sessionUser is not null
+            && user is not null
+            && installation is not null
+            && user.IsDescendantOf(sessionUser)
+            && sessionUser.HasAccessTo(installation)
+            && !user.HasAccessTo(installation)
+            && Db.Create(new InstallationAccess { UserId = user.Id, InstallationId = installation.Id });
+        
+    }
+
+    public static Boolean GrantUserAccessTo(this Session? session, User? user, Folder? folder)
+    {
+        var sessionUser = session?.User;
+
+        return sessionUser is not null
+            && user is not null
+            && folder is not null
+            && user.IsDescendantOf(sessionUser)
+            && sessionUser.HasAccessTo(folder)
+            && !user.HasAccessTo(folder)
+            && Db.Create(new FolderAccess { UserId = user.Id, FolderId = folder.Id });
+    }
+    
     public static Boolean Logout(this Session? session)
     {
         return session is not null
diff --git a/csharp/App/Backend/DataTypes/Methods/User.cs b/csharp/App/Backend/DataTypes/Methods/User.cs
index b517bbf8c..e0b47f0a6 100644
--- a/csharp/App/Backend/DataTypes/Methods/User.cs
+++ b/csharp/App/Backend/DataTypes/Methods/User.cs
@@ -1,11 +1,5 @@
-using System.Net.Http.Headers;
 using System.Net.Mail;
 using System.Security.Cryptography;
-using System.Text;
-using System.Text.Json.Nodes;
-using System.Text.RegularExpressions;
-using CliWrap;
-using CliWrap.Buffered;
 using InnovEnergy.App.Backend.Database;
 using InnovEnergy.Lib.Utils;
 using Convert = System.Convert;
@@ -91,7 +85,9 @@ public static class UserMethods
 
     private static IEnumerable<User> Ancestors(this User user)
     {
-        return user.Unfold(Parent);
+        return user
+              .Unfold(Parent)
+              .Skip(1);  // skip self
     }
 
     public static Boolean VerifyPassword(this User user, String password)
@@ -138,7 +134,8 @@ public static class UserMethods
         if (folder is null)
             return false;
         
-        return folder
+        return user.HasDirectAccessTo(folder)
+            || folder
               .Ancestors()
               .Any(user.HasDirectAccessTo);
     }
@@ -147,7 +144,7 @@ public static class UserMethods
     {
         return Db
               .User2Installation
-              .Any(r => r.InstallationId == installation.Id && r.UserId == user.Id);
+              .Any(r => r.UserId == user.Id && r.InstallationId == installation.Id);
     }
 
     public static Boolean HasAccessTo(this User user, Installation? installation)
@@ -166,7 +163,6 @@ public static class UserMethods
         
         return other
               .Ancestors()
-              .Skip(1) // Important! skip self, user cannot delete or edit himself
               .Contains(user);
     }
 
@@ -177,8 +173,8 @@ public static class UserMethods
         
         return $"{user.Id}InnovEnergy";   
     }
+    
 
-  
 
 
     // TODO
diff --git a/csharp/App/Backend/Database/Create.cs b/csharp/App/Backend/Database/Create.cs
index 875b5ddef..537192476 100644
--- a/csharp/App/Backend/Database/Create.cs
+++ b/csharp/App/Backend/Database/Create.cs
@@ -29,10 +29,18 @@ public static partial class Db
         return Connection.Insert(user) > 0;
     }
    
-    
     public static Boolean Create(Session session)
     {
         return Connection.Insert(session) > 0;
     }
     
+    public static Boolean Create(InstallationAccess installationAccess)
+    {
+        return Connection.Insert(installationAccess) > 0;
+    }
+    
+    public static Boolean Create(FolderAccess folderAccess)
+    {
+        return Connection.Insert(folderAccess) > 0;
+    }
 }
\ No newline at end of file
diff --git a/csharp/App/Backend/Database/Db.cs b/csharp/App/Backend/Database/Db.cs
index 05b3c6a7c..959322d8f 100644
--- a/csharp/App/Backend/Database/Db.cs
+++ b/csharp/App/Backend/Database/Db.cs
@@ -1,6 +1,5 @@
 using System.Reactive.Linq;
 using InnovEnergy.App.Backend.DataTypes;
-using InnovEnergy.App.Backend.DataTypes.Methods;
 using InnovEnergy.App.Backend.Relations;
 using InnovEnergy.Lib.Utils;
 using SQLite;
@@ -20,8 +19,8 @@ public static partial class Db
     public static TableQuery<Folder>            Folders           => Connection.Table<Folder>();
     public static TableQuery<Installation>      Installations     => Connection.Table<Installation>();
     public static TableQuery<User>              Users             => Connection.Table<User>();
-    public static TableQuery<User2Folder>       User2Folder       => Connection.Table<User2Folder>();
-    public static TableQuery<User2Installation> User2Installation => Connection.Table<User2Installation>();
+    public static TableQuery<FolderAccess>       User2Folder       => Connection.Table<FolderAccess>();
+    public static TableQuery<InstallationAccess> User2Installation => Connection.Table<InstallationAccess>();
 
 
     static Db()
@@ -33,8 +32,8 @@ public static partial class Db
             Connection.CreateTable<User>();
             Connection.CreateTable<Installation>();
             Connection.CreateTable<Folder>();
-            Connection.CreateTable<User2Folder>();
-            Connection.CreateTable<User2Installation>();
+            Connection.CreateTable<FolderAccess>();
+            Connection.CreateTable<InstallationAccess>();
             Connection.CreateTable<Session>();
         });
 
@@ -71,46 +70,10 @@ public static partial class Db
 
     
 
-    public static Boolean AddToAccessibleInstallations(Int64 userId, Int64 updatedInstallationId)
-    {
-        var con = new User2Installation
-        {
-            UserId = userId,
-            InstallationId = updatedInstallationId
-        };
-
-        try
-        {
-            Connection.Insert(con);
-            return true;
-        }
-        catch (Exception e)
-        {
-            return false;
-        }
-    }
-
-    public static Boolean AddToAccessibleFolders(Int64 userId, Int64 updatedFolderId)
-    {
-        var con = new User2Folder
-        {
-            UserId = userId,
-            FolderId = updatedFolderId
-        };
-
-        try
-        {
-            Connection.Insert(con);
-            return true;
-        }
-        catch (Exception e)
-        {
-            return false;
-        }
-    }
+  
 
 
-    private static async Task<Boolean> Cleanup(Int64 _)
+    private static void Cleanup(Int64 _)
     {
         await UpdateS3Urls();
         DeleteStaleSessions();
diff --git a/csharp/App/Backend/Database/Fake.cs b/csharp/App/Backend/Database/Fake.cs
index ab144c11d..ce00e87a4 100644
--- a/csharp/App/Backend/Database/Fake.cs
+++ b/csharp/App/Backend/Database/Fake.cs
@@ -70,7 +70,7 @@ public static partial class Db
         foreach (var user in Users)
             while (Random.Shared.Next((Int32)(nUsers - user.Id + 1)) != 0)
             {
-                var relation = new User2Folder
+                var relation = new FolderAccess
                 {
                     UserId = user.Id,
                     FolderId = Random.Shared.Next(nFolders) + 1
@@ -89,7 +89,7 @@ public static partial class Db
         foreach (var user in Users)
             while (Random.Shared.Next(5) != 0)
             {
-                var relation = new User2Installation
+                var relation = new InstallationAccess
                 {
                     UserId = user.Id,
                     InstallationId = Random.Shared.Next(nbInstallations) + 1
diff --git a/csharp/App/Backend/Program.cs b/csharp/App/Backend/Program.cs
index d49fa856c..d32326b7a 100644
--- a/csharp/App/Backend/Program.cs
+++ b/csharp/App/Backend/Program.cs
@@ -57,7 +57,7 @@ public static class Program
             var session = Db.GetSession(token);
 
             if (session is not null)
-                ctx.Items["User"] = session;
+                ctx.Items["Session"] = session;
         }
 
         await next(ctx);
diff --git a/csharp/App/Backend/Relations/User2Folder.cs b/csharp/App/Backend/Relations/FolderAccess.cs
similarity index 80%
rename from csharp/App/Backend/Relations/User2Folder.cs
rename to csharp/App/Backend/Relations/FolderAccess.cs
index 0cd1fa191..545647a46 100644
--- a/csharp/App/Backend/Relations/User2Folder.cs
+++ b/csharp/App/Backend/Relations/FolderAccess.cs
@@ -2,7 +2,7 @@ using SQLite;
 
 namespace InnovEnergy.App.Backend.Relations;
 
-public class User2Folder : Relation<Int64, Int64>
+public class FolderAccess : Relation<Int64, Int64>
 {
     [Indexed] public Int64 UserId   { get => Left ; init => Left  = value;}
     [Indexed] public Int64 FolderId { get => Right; init => Right = value;}
diff --git a/csharp/App/Backend/Relations/User2Installation.cs b/csharp/App/Backend/Relations/InstallationAccess.cs
similarity index 79%
rename from csharp/App/Backend/Relations/User2Installation.cs
rename to csharp/App/Backend/Relations/InstallationAccess.cs
index f898253db..c233ca953 100644
--- a/csharp/App/Backend/Relations/User2Installation.cs
+++ b/csharp/App/Backend/Relations/InstallationAccess.cs
@@ -2,7 +2,7 @@ using SQLite;
 
 namespace InnovEnergy.App.Backend.Relations;
 
-public class User2Installation : Relation<Int64, Int64>
+public class InstallationAccess : Relation<Int64, Int64>
 {
     [Indexed] public Int64 UserId         { get => Left ; init => Left  = value;}
     [Indexed] public Int64 InstallationId { get => Right; init => Right = value;}