diff --git a/OwnChar/Data/ClientServerDataProvider.cs b/OwnChar/Data/ClientServerDataProvider.cs
index abb5733..d72181e 100644
--- a/OwnChar/Data/ClientServerDataProvider.cs
+++ b/OwnChar/Data/ClientServerDataProvider.cs
@@ -1,4 +1,5 @@
-using System;
+using OwnChar.Model;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -8,5 +9,44 @@ namespace OwnChar.Data
 {
     public class ClientServerDataProvider : IDataProvider
     {
+        public bool Save(Character character)
+        {
+        }
+
+        public bool Save(UserProfile profile)
+        {
+        }
+
+        public bool Save(UserAccount account)
+        {
+        }
+
+        public bool Save(Group group)
+        {
+        }
+
+        public bool Save(PropertyCategory category)
+        {
+        }
+
+        public bool Delete(Character character)
+        {
+        }
+
+        public bool Delete(UserProfile profile)
+        {
+        }
+
+        public bool Delete(UserAccount account)
+        {
+        }
+
+        public bool Delete(Group group)
+        {
+        }
+
+        public bool Delete(PropertyCategory category)
+        {
+        }
     }
 }
diff --git a/OwnChar/Manager/CharacterManager.cs b/OwnChar/Manager/CharacterManager.cs
new file mode 100644
index 0000000..a745458
--- /dev/null
+++ b/OwnChar/Manager/CharacterManager.cs
@@ -0,0 +1,54 @@
+using OwnChar.Model;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OwnChar.Manager
+{
+    public class CharacterManager(OwnCharManager manager)
+    {
+        public OwnCharManager Manager { get; } = manager;
+
+        /// <summary>
+        /// Gets personal characters.
+        /// </summary>
+        /// <param name="group"></param>
+        /// <returns>Returns a collection with personal characters.</returns>
+        public IEnumerable<Character>? GetCharacters()
+        {
+            if (!IsLoggedIn || UserProfile == null)
+                return null;
+
+            return GetCharacters(UserProfile.Group);
+        }
+
+        /// <summary>
+        /// Gets all public ore accessable (e.g. via shares) characters from the specified group.
+        /// </summary>
+        /// <param name="group"></param>
+        /// <returns>Returns a collection with characters for the specified group.</returns>
+        public IEnumerable<Character> GetCharacters(Group group)
+        {
+        }
+
+        /// <summary>
+        /// Saves a character. If it doesn't exists, it will be created.
+        /// </summary>
+        /// <param name="character">The caracter to save.</param>
+        /// <returns><see cref="true"/> if success, otherwise <see cref="false"/>.</returns>
+        public bool SaveCharacter(Character character)
+        {
+        }
+
+        /// <summary>
+        /// Deletes a given character. If it doesn't exists, it will be ignored.
+        /// </summary>
+        /// <param name="character"></param>
+        /// <returns><see cref="true"/> if the given character has been deleted successfully or doesn't exist, otherwise <see cref="false"/>.</returns>
+        public bool DeleteCharacter(Character character)
+        {
+        }
+    }
+}
diff --git a/OwnChar/Manager/GroupsManager.cs b/OwnChar/Manager/GroupsManager.cs
new file mode 100644
index 0000000..914f7ad
--- /dev/null
+++ b/OwnChar/Manager/GroupsManager.cs
@@ -0,0 +1,50 @@
+using OwnChar.Model;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OwnChar.Manager
+{
+    public class GroupsManager(OwnCharManager manager)
+    {
+        public OwnCharManager Manager { get; } = manager;
+
+        public Group? GetGroup()
+        {
+            if (!IsLoggedIn || UserProfile == null)
+                return null;
+
+            // ...
+        }
+
+        public IEnumerable<Group>? GetGroups()
+        {
+            if (!IsLoggedIn || UserProfile == null)
+                return null;
+
+            return GetGroups(UserProfile);
+        }
+
+        public IEnumerable<Group>? GetGroups(UserProfile profile)
+        {
+            if (!IsLoggedIn)
+                return null;
+
+            // ...
+        }
+
+        public Group? CreateGroup(UserProfile owner)
+        {
+        }
+        
+        public bool SaveGroup(Group group)
+        {
+        }
+
+        public bool DeleteGroup(Group group)
+        {
+        }
+    }
+}
diff --git a/OwnChar/Manager/OwnCharManager.cs b/OwnChar/Manager/OwnCharManager.cs
index 9815578..043d1e8 100644
--- a/OwnChar/Manager/OwnCharManager.cs
+++ b/OwnChar/Manager/OwnCharManager.cs
@@ -1,13 +1,38 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using OwnChar.Data;
+using OwnChar.Model;
+using Pilz.Cryptography;
 
 namespace OwnChar.Manager
 {
     public class OwnCharManager
     {
+        // User
+        public bool IsLoggedIn { get; set; }
+        public UserAccount? CurrentUser { get; set; }
 
+        // Data Provider
+        public IDataProvider DataProvider { get; set; }
+
+        // Manager
+        public UserManager Users { get; }
+        public GroupsManager Groups { get; }
+        public CharacterManager Characters { get; }
+
+        public OwnCharManager(IDataProvider dataProvider)
+        {
+            DataProvider = dataProvider;
+            Users = new(this);
+            Groups = new(this);
+            Characters = new(this);
+        }
+
+        /// <summary>
+        /// Tries to login on the server.
+        /// </summary>
+        /// <returns>Returns <see cref="true"/> if the login was successfull and <see cref="false"/> if not.</returns>
+        public bool Login(string username, SecureString password)
+        {
+            return IsLoggedIn = true; // TODO: Change `true` to the real check.
+        }
     }
 }
diff --git a/OwnChar/Manager/UserManager.cs b/OwnChar/Manager/UserManager.cs
new file mode 100644
index 0000000..780c03e
--- /dev/null
+++ b/OwnChar/Manager/UserManager.cs
@@ -0,0 +1,52 @@
+using OwnChar.Model;
+using Pilz.Cryptography;
+
+namespace OwnChar.Manager
+{
+    public class UserManager(OwnCharManager manager)
+    {
+        public OwnCharManager Manager { get; } = manager;
+
+        public UserAccount? CreateAccount(string username, SecureString password, string email, string displayName)
+        {
+            // Create account
+            // ...
+
+            // Create profile
+            // ...
+        }
+
+        /// <summary>
+        /// Saves the current logged in user account.
+        /// </summary>
+        /// <returns><see cref="true"/> if success, otherwise <see cref="false"/>.</returns>
+        public bool SaveAccount()
+        {
+        }
+
+        public bool DeleteAccount()
+        {
+        }
+
+        public UserProfile? CreateProfile()
+        {
+            // Create profile
+            // ...
+
+            // Create pre-defined group
+            // ...
+        }
+
+        /// <summary>
+        /// Saves the current logged in user profile.
+        /// </summary>
+        /// <returns><see cref="true"/> if success, otherwise <see cref="false"/>.</returns>
+        public bool SaveProfile()
+        {
+        }
+
+        public bool DeleteProfile()
+        {
+        }
+    }
+}
diff --git a/OwnChar/Model/Character.cs b/OwnChar/Model/Character.cs
index 90b0642..a34aefb 100644
--- a/OwnChar/Model/Character.cs
+++ b/OwnChar/Model/Character.cs
@@ -1,8 +1,11 @@
 namespace OwnChar.Model
 {
-    public class Character
+    public class Character(Group group, string name)
     {
         public ulong Id { get; set; }
-        public PropertyList Properties { get; set; } = [];
+        public string Name { get; set; } = name;
+        public Group Group { get; set; } = group;
+        public List<Property> Properties { get; set; } = [];
+        public List<PropertyCategory> PropertyCategories { get; set; } = [];
     }
 }
diff --git a/OwnChar/Model/Group.cs b/OwnChar/Model/Group.cs
new file mode 100644
index 0000000..41f776e
--- /dev/null
+++ b/OwnChar/Model/Group.cs
@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OwnChar.Model
+{
+    public class Group(UserProfile owner)
+    {
+        public int Id { get; set; }
+        public UserProfile Owner { get; set; } = owner;
+        public List<UserProfile> Members { get; set; } = [];
+    }
+}
diff --git a/OwnChar/Model/PropertyList.cs b/OwnChar/Model/PropertyList.cs
deleted file mode 100644
index 08b1ee4..0000000
--- a/OwnChar/Model/PropertyList.cs
+++ /dev/null
@@ -1,6 +0,0 @@
-namespace OwnChar.Model
-{
-    public class PropertyList : List<Property>
-    {
-    }
-}
diff --git a/OwnChar/Model/UserAccount.cs b/OwnChar/Model/UserAccount.cs
index a2f36d6..ff69c91 100644
--- a/OwnChar/Model/UserAccount.cs
+++ b/OwnChar/Model/UserAccount.cs
@@ -1,17 +1,17 @@
-using Pilz.Cryptography;
-
-namespace OwnChar.Model
+namespace OwnChar.Model
 {
-    public class UserAccount(string email, string username, SecureString password, string? displayName)
+    public class UserAccount
     {
         public ulong Id { get; set; }
-        public UserProfile Profile { get; set; } = new(string.IsNullOrWhiteSpace(displayName) ? username : displayName);
-        public string Username { get; set; } = username;
-        public string Email { get; set; } = email;
-        public SecureString Password { get; set; } = password;
+        public string Username { get; set; }
+        public string Email { get; set; }
+        public string Password { get; set; }
 
-        public UserAccount(string email, string username, SecureString password) : this(email, username, password, username)
+        internal UserAccount(string email, string username, string password)
         {
+            Username = username;
+            Email = email;
+            Password = password;
         }
     }
 }
diff --git a/OwnChar/Model/UserProfile.cs b/OwnChar/Model/UserProfile.cs
index ea19eda..767b19f 100644
--- a/OwnChar/Model/UserProfile.cs
+++ b/OwnChar/Model/UserProfile.cs
@@ -4,5 +4,6 @@
     {
         public ulong Id { get; set; }
         public string Name { get; set; } = name;
+        public UserAccount? Account { get; set; }
     }
 }