@EM1 ,
As I understand it so far.
You have two SharePoint Lists (List1 and List2).
You have a Form connected to List 1. This List contains a Single Line Text field (Rubrik).
In List 2, you have a field called Title, and you have a LookUp field to List1 (Typ).
In your Form, you have a "parent" dropdown control which displays the Rubrik field in List 1.
In your Form, you also have another "child" Dropdown control which displays each item from the Title column from List 2, but filtered depending on the selected item in the Parent dropdown.
Is that correct?