diff --git a/Assets/Scripts/InventoryStuff/DisplayScrolls.cs b/Assets/Scripts/InventoryStuff/DisplayScrolls.cs
index 71e528c558185f120415f69e560f36f830f8f0be..a9ec4ddcd40579c81b51392a78755b72348b1695 100644
--- a/Assets/Scripts/InventoryStuff/DisplayScrolls.cs
+++ b/Assets/Scripts/InventoryStuff/DisplayScrolls.cs
@@ -42,6 +42,6 @@ void BuildScrollGUI()
 
         REST_JSON_API.Scroll preferredStartScroll = AllowedScrolls.Find(x => x.label.Equals(preferredStartScrollName));
         if (preferredStartScroll != null)
-            ScrollDetails.Instance.SetScroll(preferredStartScroll);
+            ScrollDetails.Instance?.SetScroll(preferredStartScroll);
     }
 }
diff --git a/Assets/Scripts/MMTServer/CommunicationProtocoll/MMTConstants.cs b/Assets/Scripts/MMTServer/CommunicationProtocoll/MMTConstants.cs
index 9b4a1fd1401547befb0f568d2af0d20a08bbb89a..1c21f66dfd73d6c347ef3c7c2cc1c018fee9fddf 100644
--- a/Assets/Scripts/MMTServer/CommunicationProtocoll/MMTConstants.cs
+++ b/Assets/Scripts/MMTServer/CommunicationProtocoll/MMTConstants.cs
@@ -80,6 +80,7 @@ public static class MMTConstants
         public static readonly string ListEnd = "http://gl.mathhub.info/MMT/LFX/Datatypes?ListSymbols?nil_constant";
 
         public static readonly string AddRealLit = "http://mathhub.info/MitM/Foundation?RealLiterals?plus_real_lit";
+        public static readonly string AddArith = "http://mathhub.info/MitM/core/arithmetics?RealArithmetics?addition";
         public static readonly string MinusRealLit = "http://mathhub.info/MitM/Foundation?RealLiterals?minus_real_lit";
         public static readonly string InvertRealLit = "http://mathhub.info/MitM/Foundation?RealLiterals?inv_real_lit";
         public static readonly string TimesRealLit = "http://mathhub.info/MitM/Foundation?RealLiterals?times_real_lit";
diff --git a/Assets/Scripts/MMTServer/CommunicationProtocoll/SOMDocToLambdaExpression.cs b/Assets/Scripts/MMTServer/CommunicationProtocoll/SOMDocToLambdaExpression.cs
index ae2b510da774a981f03851e50d1c44f12fb4690b..3db15b58e461ea133d8f747de8b95fc1431eefcf 100644
--- a/Assets/Scripts/MMTServer/CommunicationProtocoll/SOMDocToLambdaExpression.cs
+++ b/Assets/Scripts/MMTServer/CommunicationProtocoll/SOMDocToLambdaExpression.cs
@@ -183,6 +183,8 @@ protected static class SOMDocToLambdaExpression
         {
             { MMTConstants.AddRealLit,
                 ExpressionType.Add},
+            { MMTConstants.AddArith,
+                ExpressionType.Add},
             { MMTConstants.PointAddI,
                 ExpressionType.Add},
             { "AddAssign",
diff --git a/MaZiFAU - MainMenue - Windows, Mac, Linux - Unity 2021.3.5f1 Personal _OpenGL ES 3.2_ 2024-01-23 14-08-46.mp4 b/MaZiFAU - MainMenue - Windows, Mac, Linux - Unity 2021.3.5f1 Personal _OpenGL ES 3.2_ 2024-01-23 14-08-46.mp4
new file mode 100644
index 0000000000000000000000000000000000000000..7ae507d12d88b9cbe0cd28a8206f80bccae620e3
--- /dev/null
+++ b/MaZiFAU - MainMenue - Windows, Mac, Linux - Unity 2021.3.5f1 Personal _OpenGL ES 3.2_ 2024-01-23 14-08-46.mp4	
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:843344a8887ee99d24c3cc2f91884587f4804275b53ae4a58fe738993f2c5e4f
+size 145891733