Single-family house with a 75 sqm granny flat

Hello , Thank you for the summary. It can also be referred to as a two-family house, whereby the criteria for a granny flat are met. I had hoped for suggestions and ideas in this forum and not to be portrayed as "complaining." I try to answer questions as best as I can. It is important for us to have the living and dining area and the granny flat on the ground floor, but I also realize that we are reaching limits with the property here.

I would consider separating the house and the garage. The garage costs a lot of money. Partially built over, insulation, etc.

made a good point about using the slope. That would also provide some relief. Why did you reject that?
Basement: granny flat with west-facing terrace
Ground floor: your living rooms with south-facing terrace
Upper floor: bedrooms
One more level, but cheaper construction (simple rectangle)

As a note – age-appropriate is a flexible term – what do you imagine by that?

I would consider separating house and garage. The garage really costs money. Partially built over, insulation, etc.

Yes, I had thought about that too, but where to put that damn thing?

If necessary, none at all

One gets annoyed daily about a living space that is too small and unsuitable

If necessary, none at all

You get annoyed every day about a living space that is too small and not suitable

Yes, but OP writes that there is zero parking space on the street. I don’t necessarily see a garage either, but even pure parking spaces are not available here. Simply unsuitable for the wishes for the property.

I clearly see the problem here as well, that for a lot of money you build 2 compromises that end up both being bad. In my opinion, 2 multipurpose rooms on the ground floor are one too many here. Rather, I could imagine locking the "old ones" in the attic and building an elevator in the stairwell. Or half-burying the house with a basement for the oldies and a half-stairway to the terrace for the rest of the family. As it is now, I would simply miss the light in the rooms too.

I try to answer questions as best as I can.

Well then, you probably overlooked this one?: https://www.hausbau-forum.de/threads/grundrissplanung-unbedingt-vor-Beitrag-Erstellung-lesen.11714/