Thanks for the answer and sorry for the missing information.
I have firmware 22.214.171.124A installed. I cleared the cache, but it doesn’t help.
Maybe I have an idea why I have this problem. I bought the phone with firmware 4.5 and rooted it with busybox and supersu. Then I have frozen the apps Cloud-Service and MzAccount and a lot of other apps that I thought I wouldn’t need (weather, reader, recorder…).
After this, I updated to the latest firmware and now the root is no longer available, so I can’t unfreeze the apps again.
No clue how to get out of this situation as I ned obviously root rights to unfreeze these apps.