How can I take square meters from the bathroom without damaging the ground floor?
Why do you find the arrangement of the objects unfortunate?
Do you also have a half-landing staircase? What dimensions do you have and what would you do differently?
I think the "problem" is precisely that I don’t have 160 sqm, but only 151 sqm of living/usable space.
The ground floor benefits from it too. Just changing the upper floor doesn’t really work.
The alignment of the objects and the toilet directly next to the washbasin. (This is much better solved in the other floor plan you are using for comparison.)
No half-landing staircase, a standard half-turn staircase...
No, the 151 sqm is not the "problem," but rather the design of the floor plan.
The other floor plan, which you have already discovered (with an office between the children’s rooms), is overall much better executed. (Okay, I see the children’s rooms there as too small, but the rest, especially the kitchen access from the hallway, is good.)