Greetings jakobzischka,
We understand when listening to Spotify, the music skips. We'd like to help.
Does this only happen when you're listening to music in the background?
Is there any improvement if you power off and restart your Mac? Often this can help resolve lagging and other issues.
If you restart your Mac in safe mode does the same thing happen? Safe mode prevents your Mac from loading certain software as it starts up, including login items, system extensions not required by macOS, completes a basic check of your startup disk, and clears cache. Test while using the applications in safe mode, then restart and see how your Mac responds after this.
How to use safe mode on your Mac
Cheers.