how did you do it? My co-founder is in a similar situation, and his tax-lawyer said the only way was via a trust - they also have a German holding. Do you have to declare that somewhere? or how does this work? Thanks!

I can't give more specific information about my situation, but I would recommend contacting one of the companies that has a public article on the "Wegzugssteuer", for example the one I linked in the first comment. That way you know you get someone that actually knows how to deal with this.

My first tax advisor barely even knew about the Außensteuergesetz and almost got me into larger trouble because of that. I'd guess since this law only affects a tiny portion of the population you really need someone that specializes in it.

If they specialize in it they'll have done this many times before and you can just use their pre-made constructs. Then the main issue is avoiding getting squeezed by them.

Trusts dont exist in Germany . Did you mean a foundation e.g family foundation ?