Thank´s for your response!
Following is the extract of the data model:
I have a index unit to show all hotels. These index unit is connected to a page to open a form to modify the attributes of the hotels:
Following the list of hotels and the modify form of the application:
The problem is now that (as you see in the alst screenshot) the preselection for the Region and City is not working.
Have you any idea how to change this?