Hey, first of all, thank you very much for your answers and effort.
You actually hit many of our concerns right on point. Unfortunately, the thread title with the forced points doesn't come from nowhere. I also started the thread with the thought of hearing a different opinion here and there. I have the feeling that we are getting too tense about some points.
Maybe for those interested, now a longer text with our thoughts that we had during the planning:
-We really travel a lot, but unfortunately there is nothing here worth preserving, except for the planned garage, even remotely. The garage is an extension (1 story/flat roof) that was added significantly later to the old house. It is made of 30cm Poroton blocks (T12-14), a solid ceiling and was already planned for an additional floor (foundations etc.) It has a window front facing the street in the width of the planned garage door, meaning that only the parapet would have to be removed for the garage door. The neighboring house on the right is two stories high in this area with a gable roof, gable facing the street, so adapting the height here and adding a floor makes sense. Otherwise, we would be looking at the not really nice, very high facade of the neighbor. The entire orientation of the building is therefore away from the neighbor due to the neighboring boundary development on both sides. Ultimately, it's also a cost factor, saving demolition and with manageable effort gaining a good 40m² of living space. Allow me a sharp remark here, I think for what the additional floor costs me, many do not place a double prefabricated garage next to their city villa.
But of course, we subsequently create the forced points regarding the exterior dimensions of this area.
-Children/children’s rooms
At the moment there are no children yet, but they are definitely planned. Whether it will be 0,1,2 or 3 will show in the future. I actually have a problem with this forced planning of 2 children’s rooms directly next to the parents’ bedroom. Children also grow older, this thought, I have to admit, had a bigger influence on the floor plan than the needs of the children in the first years of life. In some standard floor plans, I wouldn't want to be a teenager again.
With one child, the drywall between the rooms could be omitted => all good. Also in the case of no child, or the children have left the house, I find the large room then very usable. Even though it was not a planning principle for us, if in old age you depend on a caregiver, this slightly separated area with its own small bathroom is well suited.
With 2 children we would have the shown variant, certainly unfortunately not optimal.
With 3 children, one could easily separate and halve the planned office and thus get a 3-room layout. This would still largely fit the concept of the children's area in the front part of the house.
For me these thought processes were quite important, since without a basement or attic there is no extension or conversion potential.
-Light was a big topic, unfortunately no window possible to the east, to the south is the street and entrance area, we deliberately tried to arrange individual rooms according to their use. Rooms with no light requirement, or where it is most tolerable, are placed in the darker areas. Living/dining and kitchen area consciously open to the back of the house towards the garden etc. Unfortunately, the large window front then faces north and west. I know some houses with this orientation and never found them too dark. So far, I was rather e.g. an opponent of strict southern orientation. I know it rather that about half of the time some kind of shading is used. Skylights were also already a topic. The attic is quite important to us as storage space, plus the ventilation system is installed there. Also, there was an idea to keep the roof surface of the gable roof facing the street completely homogeneous. (Even something like putting the bathroom vent tiles on the back side) => The gable roof area should, due to its simplicity, better adapt to the Bauhaus-style extension. We also already considered the variant of equipping the roof surface in the hallway area completely from eave to gable with a light strip, but cost/benefit stopped us above all.
Maybe all this sounds a bit like justification, but that is really not the intention.
I have to say this forum is great and we are grateful for every answer, some of which are really helpful.