Floor plan single-family house approx. 180 sqm

But the garage may then be a maximum of 9m long and 3m high. And isn't it higher than 3m because of the roof?

It would be about the wall, that is, "eaves" height.

The roof of the garage of is indeed hipped. So with the wall height, no problem.

Thank you all for the numerous suggestions and ideas!
Over the weekend, we gave a lot of thought to our floor plan. We would now like to keep the exterior dimensions at 10.5 m x 11.0 m. We have revised the existing floor plan ourselves again according to our ideas. We experimented a bit with different stair shapes and arrived at the attached result. The guest room has been removed (not absolutely necessary) and the garage has been moved to the front (it could also be pushed a bit further forward). We are still somewhat uncertain about the ceiling spans here.

And where does remote work take place then?

And again the question, should the garage be used for 2 cars? If yes, how should bicycles etc. be stored then?

We have been thinking a lot about our floor plan over the weekend.

Me too, namely: what kind of Aztec demons are those at the entrance?

For the bicycles, a bike shed/garden house would do from my point of view, but you still lack a room now. And that with 180 m2? I wouldn't make any compromises there. Take a look at the Viebrockhaus Maxime 810 II. Slightly smaller than your house and significantly better laid out with additional rooms. There is a reason why the standard houses fit the typical home builder very well. After all, not everyone is architecturally skilled enough to create a floor plan themselves.