Optimize new single-family house floor plan

Putting a room in the basement is a good measure. It could also be the guest - presumably they are there less often than one works at home.

This is an additional attic.

This is an additional attic.

Thanks, then the suggestion with the galleries for the children can also be forgotten.
I thought the basement was a good idea.

But this time we didn't look for a floor plan as a best-fitting basis, but started from scratch

Alone, I lack belief. I see at first glance and without glasses that the advice to start on the upper floor was ignored. Instead, a penthouse level has now appeared. Poor child 2 not only has, by feel, the smallest room, but also has to hear that it supposedly has the middle one – nominally one and a half square meters more than child 1, but at least just as much less furniture space. And you almost certainly didn't start with a room plan; among other things, the penthouse level is evidence.

Giving up symmetry from the outside offers you the possibility to move the kitchen window to where the optimal kitchen allows.
The symmetry of the house front either leads to a window in the guest room that is too small or a window in the guest WC that is too large. Here too, it is better to think from the inside out.

Symmetry in the hands of amateur planners is in any case the greatest architectural love-killer, but at least I did not recognize any at first glance here
Ceterum censeo: I am in favor of introducing a "pharmacy-only" prescription for symmetry

Alone, I lack the belief. I see at first glance and without glasses that the advice to start with the OG was ignored.

We did not start with the OG. Was that written anywhere here? Then I probably overlooked it.

And you quite certainly did not start with a floor plan

What does floor plan mean in this context?

We did not start with the upper floor. Was that written somewhere? Then I must have overlooked it.

(but still built the upper floor on the ground floor, a forgivable amateur mistake).

.

What does room plan mean in this context?

First math homework, then the fun of painting. So make a table with rooms and their sizes, and the sums of all rooms in the upper floor and ground floor must be about the same ("town villa") or, depending on the state building code, less in the attic floor than in the ground floor ("one-and-a-half-story"). If you skip this step, a room ends up on the roof rack aka attic floor. Upper floor larger than ground floor is not a problem (provided an overall area of 2x upper floor complies with the values "floor area ratio" and "budget"), then you just "waste" a bit of space on the ground floor. Typically, the upper/attic floor is planned as bedrooms and the ground floor as living space, and it is easier to first plan the more finely structured floor and then derive the other from it. (Attention hillside property owners: the mnemonic "upper floor before ground floor" cannot be directly transferred to the constellation of ground floor and basement!)

Poor child 2 not only has what feels like the smallest room, but also has to listen to being told it actually has the middle one - nominally one and a half square meters more than child 1, but at least as much less furnishable.

Why does it feel like the smallest and less furnishable - because it is more rectangular than square? For child 2, the internal measurements 2.5m * 4.8m = 12 sqm (plus narrow entrance) are indeed more than the 11.9 sqm of child 1 (including door).

And you most certainly didn’t start with a floor plan, among other things the stepped floor is evidence.

Additional info: In the area, a third floor must be built, which was not yet clear before. Therefore, our conclusion was to move some things there.