Planning single-family house 210 sqm living area. Without basement

Hello,
we have now made some initial fundamental decisions, planned something, and request constructive criticism.

Bebauungsplan/Einschränkungen
Plot size 800 sqm
single-story, plot 180 sqm, 18x13m building field, 25° roof pitch, gable roof

Anforderungen der Bauherren
Style modern, 2 full floors with open roof concept, no basement, 2 bay windows that become roof terraces on top, high ceiling heights (at least 2.70m downstairs, open upstairs, up to 6m wall height, 9m ridge height possible), total approx. 210 sqm living space.
Planned for 4 people
Office: rarely home office
Overnight guests per year, none
Open kitchen with island
Number of dining seats 8
Fireplace
Double prefabricated garage separate from the house with small annex as storage
Garden shed as storage

Hausentwurf
Who designed the plan:
- mix of model house + do-it-yourself + planner

What do you particularly like? Roof terraces on the east and west (sunset), large open dining/living/kitchen area, orientation according to the cardinal directions, fireplace in the room, view of the staircase as a highlight, south side with venetian blinds, 3 doors (2 sliding, 1 normal) to the south terrace, separate area for parents with sauna, niche in the hallway for wardrobe.

What do you not like?
Children’s rooms possibly too small with 12-13 sqm. However, it would be possible to build a gallery in about 10 years, when the kids are old enough, which could create additional space. The gallery could then be used as play or sleeping space. Considering maybe extending the house by 1m and reducing the bay windows, which would create more space for the kids if necessary, or alternatively shrinking the upstairs hallway? Personally, 10 sqm was plenty for me at that time.

Wall thicknesses were taken into account in the sqm (only the staircase not yet deducted/calculated out)

Price estimate and personal budget excluding exterior work, land, and ancillary costs: 600-650K €. Approximately 100K € are also planned for ancillary costs + furniture + exterior work.

Aligned the partition wall on the upper floor. This gives Child2 13.7 sqm and the children’s bathroom 6.6 sqm. Hallway still sufficiently large

I would have the "part" planned by a proper architect. It seems to me as if the exterior walls were simply drawn here and there, where one cannot estimate the room sizes, thus bloating an existing design.

90 sqm for the open-plan living area is quite a lot; is there really "only" a hallway space, meaning the stairwell, in the middle? The fireplace is also placed very "airy"... where would the fireplace be upstairs?
The visual axis door/stairs does not match. It looks wrong and skewed.
If the pantry is one meter wide, then it is too narrow.

No children yet? The location of the stairs reveals it, at least no teenagers in the house. So the design is not family-friendly.
Guests would be there for everyone.
Also, compared to the house and the 90 sqm room, the children's rooms are actually quite small and cramped. Considering children live in their rooms and not in the stairwell...
A gallery at 25 degrees is also not a fully usable room - no standing space, no making beds...
Regarding the roof terraces: who is supposed to and allowed to use them and when? You don’t want to watch the sunset in front of the children's room, do you? And what about child 2?
Bedroom: too narrow for a 2-meter bed, too much window area.
By the way, I recognized your open roof truss thread on the upper floor ;)
I am still of the opinion that the floor plan is not suitable for it.

Too many windows. And a toilet on the living room wall? The master bedroom is way too small and cluttered. Kids' rooms have far too little storage space. Kids have a lot of stuff! With the number of windows and roof terraces and high ceilings and open roofs, you won't manage within the budget either.

Technology on 11 sqm plus housekeeping can also be significantly too small depending on the type of heating and ventilation and electrical requirements.

And a toilet on the living room wall?

Who starts at the back, putting the cart before the horse? ;) Yes, it needs to be rotated to the other pipelines. But the design will have to develop anyway.