So, after some time has passed, here is a brief update.
Currently, we are at the point where we can say that the building structure itself is tailored to our needs. As a result, it is just over 24m in total length. The gross floor area amounts to around 710 sqm. Based on this and the already determined layout (underground garage including cellar / 2 floors + attic floor with flat roof / number of bathrooms / elevator / etc.), the current cost calculation has been developed in parallel.
Since we didn’t really like the proposal for a complete glazing of the balcony and roof terrace, a different concept will be presented to us next week (we are keeping an open mind). Our change requests are still incorporated in the window planning (such as size / location and so on). However, since we have calculated this position generously, it should not be a problem, for example, to have floor-to-ceiling window / terrace elements. That’s also why I asked a question in a subforum. In any case, it will come down to wood / aluminum. The HLS topic is now being dealt with more intensively. We only have gas as an option for supply, so a combined heat and power plant is under consideration.
There is also a short-term appointment with our tax advisor and financial advisor to finalize the "surrounding matters" and find the truly right way.
If all goes well, the building application can be submitted in the next 2 months.
However, this will still require many appointments, many discussions, and a lot of time!
Best regards and many thanks to the forum, which always provides good advice.