Thanks for all your replies @John Vere It happened at the very beginning of a new project, so there were just like one instrumental track(mp3) and 2 or 3 tracks whith some test vocals. At this point I didn't add any effects or plug-ins to the tracks. On older and larger projects were I had more tracks and already added some effects/plug-ins there was no problem with the waveform while recording.
Even if i delete all four tracks from the project where the issue occures and add only a new single track and hit record, there is no waveform altough it records audio and draws the waveform immediately after I hit stop. @Andres Medina & @rfssongs I tried this, turned it on and off, nothing changed. But on a new project this setting works as it should and I can show/hide the waveform.
I have found out, that I can copy all 4 tracks from the problematic project and paste them in a new project, then the waveform works.
However, I have no idea what to do if the problem occurs at a later point in the project when i have already added various effects, Plug-Ins and settings 🙈. I don't think I can copy all those too.
Maybe I will test some things and try to recognize what happens before the waveform-problem occures👀
Thanks so far