zzz Thanks a lot for your answer. I already tried Ture Dialer and another one I can't remember the name right now. Both couldn't show the history. I will try other ones for sure.
And yes, I managed to see the call history with a text editor on my PC.
But man, I'm really disappointed and sad right now. I was so hyped with Graphene OS and have used it for two monts. But this is a feature I can accept to not have it on a private case, but for my work it is necessary.
I hope, that there might be just a simple setting I needed to activate or else.
I think I have to give up on my privacy journey and use the stock android or use an iphone ...