Single-family house with 190 sqm - What do you think about the design? Feedback?

Then deal with the actual apartment - at least as a drawing exercise, but maybe also as inspiration for the fellow discussants (?)

Which East Frisian joke was incorrectly translated into Bavarian? - considering the savings, one almost has to say "perverse costs extra"

I'll take a photo of the thing in the next few days, otherwise no one will believe me.

Then engage with the current apartment - at least as a drawing exercise, but maybe also as inspiration for the fellow discussants (?)

I wouldn't know how to engage with the current apartment - 200 sqm old building Düsseldorf city center; 3.5m ceiling height, 60cm brick wall, all on one level;

I would hardly plan anything else unless it was necessary. And unfortunately, something like this can no longer be built today.

I wouldn't know how to occupy yourself with the apartment

For the two reasons I have already mentioned. You don't know any apartment better than this one, and once you have seen it through the eyes of a folding ruler and traced it, you are calibrated in terms of dimensions. In the next step, you cut it out and change it where it doesn't fit so well. And then you arrange these rooms together in different layouts. Gain insights with scissors that you can't get with a mouse. Even then, you won't agree with every criticism of your plan, but you will probably understand it much better so that you can implement it creatively.

But that already fails because 200sqm on one level are laid out differently than if I spread them over two floors and still need a technical room and a staircase somewhere - at the moment we have several rooms that are 25-30sqm large and are only used as an office and entrance area; such things no longer exist today and I don't really need them either

But that fails because 200 sqm on one level are laid out differently

Nothing fails at all, you fix that by cutting out and rearranging.

Because you compared your costs and complained a bit in the other thread: the question about the specification of your construction site is still unanswered. There is a remarkably large price difference between Echterdinger Höhe and the deepest Alb. Moreover, the statement is not correct; your costs were dismissed as "absolutely impossible," but I explicitly pointed out that it is possible.