Is rotating the house an option? Assuming garage at the edge of the property and unfortunately only a desk corner instead of an office inside. But otherwise nice rooms upstairs possible.

Yes, indeed better rooms are possible there, we had already considered it at the beginning, but at that time the double garage was still supposed to be fully integrated into the house, which would not have allowed edge development.. it is still quite a massive 16.8m frontage, but we will think about it again. Of course, it also slightly restricts the accessibility of the property..
We have also struggled often with the study, whether it really has to be there, but since my wife is a teacher and will not always definitely have her own classroom where she can store things, a lot of materials and paperwork accumulate over the years that need to be stored, apart from working hours at home.. Only a desk alone is rather no option.
The second child is not yet quite certain, until then we wouldn’t initially have a „storage problem“ due to the free room, but afterwards it might become problematic, an extra equipment shed + spacious garage extension is probably to be expected then.
How do you actually see the 5.75m interior dimension for a double garage, more on the lower limit?
We have another appointment with the architect tomorrow, a lot will be clarified again, also regarding the wall thicknesses.. he wants to propose a few floor plans again, with a straight staircase and wider upper floor and one with a half-landing staircase similar to yours, as well as mirrored with the garage on the east.
By the way, what I forgot to mention: to the west, on the property after next, there is an about 12m high old building with 3 room-high floors about 30m away from our boundary that is being renovated and will contain 6 large condominiums with balconies.
Of course, we approach this with the house and terrace by mirroring the garage by 6m, which was initially my reason to position the garage on that side without considering the advantages of the west side..
But privacy screen or fence will be put up either way.
Many thanks again at this point, we will report back with news in the next few days..