

Wettbewerbsverbot is yet another issue, when you switch to a competitor. Say I’m programming fullstack for my employer and start a Web App as hobby. How do I prove that this is not based on training my employer paid for? If it is in a totally unrelated field it would be easier.

That’s what they use to say here, too.
Still inventions and „creations“ while employed have their own law and regulation. I don’t know them in detail, but I understand that it can be fuzzy and complicated.
https://de.wikipedia.org/wiki/Arbeitnehmererfindung