Restarting my iPad did the trick. As i said, this problem did not come by using an iPadOS-Beta as I am personally using the newest stable version 15.7. Although the app does work, you should look at this problem because it directly came a hour after downloading the app.

Alright, i will try it in a couple of hours as I am currently not at home.

No, i am Not using the iPadOS Beta, i am using the newests stable Version 15.7.