Support hanging and filling - Additional costs?

If I understood you correctly

I don't know. So, three regulations must be observed: the development plan (planning law), the state building code (building regulations law), and the neighbor law (private law). According to the development plan, both the garage and the terrace and even the terrace on the garage are permitted on the boundary or at any distance from it. According to the state building code, the garage is permitted on the boundary or at least 1m away under the conditions specified in §6, paragraph 10. However, no rooftop terrace may be located on it, because for this §6, paragraph 8, no. 6 applies Terraces that are arranged no more than 1 m above ground level or including their railing are no higher than 2 m. This rooftop terrace does not meet these conditions and thus triggers setback areas, which must be at least 3m deep. I will omit neighbor law, as it is most likely irrelevant in your case.

Ah perfect. Thank you very much!

Then at least we have a concrete plan and will see what comes of it in the end.