Hey there Marko2 and Hess87,
This issue sounds pretty frustrating to deal with, so I'd be happy to help you out. Let me just ask some questions to better understand what's happening:
If possible, try setting up the Chromecast using a different device, such as another phone or tablet, and see if the problem persists. I look forward to your responses, and if you have any other questions or concerns for me, please let me know.