Initial planning single-family house with granny flat on 600 m2

Well, if only one could properly assign something. And, if one knew why a 10 m wide house can fit on a 13 m wide plot. What about the otherwise at least 3 m distance? Can the garage be so close to the street?

Regarding the basic dimensions, I am also still undecided. I think from the current floor plans, it would also be possible to come to 8 m x 12.5 m. According to an acquaintance, I need 2.5 m distance from the neighbor boundaries in BW. Probably less to a public street. If necessary, I would have to request a building encumbrance from the hillside owners. The old building even currently has a boundary encroachment.

And, if one knew who is supposed to live in such a dark granny flat. Bedroom without windows? Bathroom accessible from the living room? Only west light? Who is supposed to rent that?

Windows in the bedroom are planned on the north side. On the south side, there would still be a window in the office. Overall, I am completely unsure here.

I understood correctly that the ground floor is practically dug into the hillside in the east.

Yes, the ground floor is in the hillside in the east and the hillside is currently "walkable" at the level of the 1st floor through a retaining wall.

Space requirements on the ground floor and first floor: See draft

This is not conclusive for me or mixes up cause and effect. You should explain how you want to live, what needs you have as a family. From that, the floor plan results.

The apartment is intended to serve as a retirement home and therefore should be on the ground floor.

I have to question that in this context – almost traditionally – why is the apartment needed? You are 30+25 years old and (are) building for an event in 40 years? So much happens until then, free yourselves from this constraint.

You are 30+25 years old and are (ruining) for an event in 40 years? So much will happen until then, break free from that corset.

By then, the dementia risk factor of fear of change will have been researched so far that this basic attitude of staying in a once acquired home until the last breath will be unlearned.

That is not conclusive to me or it reverses cause and effect. You should explain how you want to live, what needs you have as a family. The floor plan results from this.

Yes, all that is missing - this won’t work like this.
So far, I don’t understand what the priorities and needs are.
Somehow, I also can’t match the floor plan drawings with the elevation drawings.

My opinion Knock the floor plan into the bin Remove the granny flat You’re sinking a six-figure amount for maybe possibly and then it still doesn’t fit. The problem is solved with a stairlift. The one from the commercial doesn’t even cost five figures for one floor if I remember correctly. You have to carry every bottle of water, every packet of pasta, and the children upstairs for the next few years. I find the floor plan too deep for the plot. A rectangle would fit better. The upper floor the children’s rooms are cut awkwardly

Yes, all of that is missing - this won't work like that. So far, I don't understand what the priorities and needs are. Somehow, I also can't match the floor plans with the elevation drawings.

Me neither, that's why I didn't respond. The elevations are of the old building that is being demolished and have nothing to do with the new building.