Floor plan design single-family house (urban villa) approx. 140m² (3 children's rooms)

Yes, the T has to go. The dressing room doesn't work: it is too narrow. Under the stairs: what do you mean? How much cupboard should fit in there? You can afford living space for 4. That's great! But why would you want more than you can afford? I'll just say: Hartz4 recipients get frowned upon,... just think about it briefly. You don't have to cram the place now, it will already be full enough with the children's friends.

That is "half the battle won," if no one mourns the T-bath. That makes replanning much easier.

Take a look here: - Zaba12 also has three children's rooms, and only 1/2 m more house width, maybe you can find some inspiration there.

The house will actually be built like that :-p. Over the next 3 days, the neighbors' signatures will be collected and then the submission planning will be submitted in the exemption procedure. The long development saved our asses regarding the child construction grant, because we could have had it approved a year ago, as you can see from the date of my thread :-p

Can’t you leave out the "Ausbuchtung" in the upstairs hallway and then move the guest room wall to the left to make both children's rooms about the same size?

Best regards
Sabine

Apart from the budget, I don't think the thing is bad.
A few key points:
How big is the shower in the bathroom?
Otherwise, the ground floor is quite nice. It is a relatively small house. You shouldn't expect too much – it's not necessarily a top performer in my opinion, but solid.

Upper floor: I don't see how to enlarge the tiny room with this staircase. On the ground floor, the staircase fits quite charmingly, but for the upper floor, it is inappropriate. Possibly a half-turn staircase could solve the problem.
The dressing room is too narrow – better to have another storage room and integrate wardrobes in the bedroom, see sketch.

I find the position of the walls as Katja has shown very successful for the size. You won't be able to get more out of the floor plan above because of that.

Ok, quite a bit can be stored in the attic.

Please make sure you are clearly told what is included in the fixed price. I fear there will be one or two nasty surprises.

Despite everything, I would reconsider the room on the ground floor. At first, it can be unused or used as an office/guest room. Only if a third child arrives will that be an option.
And then I might have to sleep on the ground floor for a few years.
As already pointed out several times: the walk-in closet doesn't work like this, and then the entire layout on the upper floor doesn't fit, because you do need a wardrobe. Katja's layout is definitely much better and an option for 4 bedrooms on the upper floor.

I would move the living room entrance door to the left. This will create more space for the living room TV wall.

Best regards
Sabine