Hi chaimp! Thank you very much for your answer! It helped me to understand to things that were missing: I did not turn on the developer mode on my iPhone I had to change the bundle-id in my settings (I was not aware, that the bundle id seems to have the requirement that it contains an URL; I just used random characters that were not working.... Changing these to things everything works fine now! Thanks again!

I was not aware, that the bundle id seems to have the requirement that it contains an URL; now, using an existing URL with the suffix of my App-Name, everything works fine.