Planning of a single-family house (basement + ground floor + upper floor) on a 480m² plot

Once again, the straight staircase triumphs over reason.. the house is too small for this type of staircase.

What else I notice: Why did you actually place the garage in the west and thus have not a single west-facing window on the ground floor? That is really a shame! If you really want help here, we need a site plan with [Baufenster]!

And where has the desired guest room on the ground floor disappeared to?

We still have to design the basement,

You are still dreaming and very much focused on "designing." For floor plan criticism, it's definitely too early for me; this is a show house for Mr. & Mrs. Very-Rich.

Is the living room in the hallway?

I think that's called a "foyer" when a seating area is in the entrance hall :)

How about as an inspiration for the floor plan using the show homes from Regnauer or Weiss from the show home park in Poing? They have the straight staircase and the basic room layout that you imagine. You could transfer the variant with the sauna from the Regnauer house to the Weiss house and implement the balcony above the technical room there (provided it fits the plot).

Unfortunately, we are still clueless about the plot, but both houses (and Regnauer’s "Liesl" at Chiemsee) pleased us a lot during the visit and quickly made us abandon our "we need a 200 sqm palace" view.

For this "Grundriss" :oops: the name of a user here fits quite well: "HilfeHilfe". :D