Floor plan of a single-family house 240 m² with a partially built-over garage

Exactly that is what I expected after 3 months. Well, some people just take their time.

I can’t detect any position statement of a further planning process from the latest sign of life of the OP yet, and therefore assume ongoing stagnation of the so-called “still fruitless reflecting” of the discussion. There would be (I have several competitors, and even many more rivals) enough freelance consultants for all uncertain prospective builders [hheh].

Maybe they are waiting for falling prices.

That would be unwise, however; Godot will arrive sooner. Whoever wants to raise prices (for money or other building materials) will also find reasons for it. A potential (but unlikely!) lack of real or apparent causalities from the world politics and economy section of the daily newspapers would not put this phenomenon to rest. Far too many prospective builders compare the future construction costs with those of the past instead of looking at the development of housing costs from rental to owner-occupied housing. Thus, the prospective builders stand in their own way and turn into hesitant builders. The housing market is pleased. As my motto “Build now” already says, I see the relative attractiveness of homeownership far away from any downturn.