Floor plan of a single-family house with 4 children's rooms and a separate apartment

Hello everyone,

after much back and forth, we have decided to build a house with a granny flat.
Recently, I received the floor plan draft from our architect. Due to the small plot size and my lack of experience, I would like to gather your assessments/improvements with this.

Bebauungsplan/Einschränkungen
Plot size: 435m²
Slope: no, but it must be filled up flush with the street
Site coverage ratio: 0.25
Floor area ratio: 0.55
Building window, building line and boundary: 9 x 12.11
Edge development: garage -> yes
Number of parking spaces: 2
Number of storeys: 2 full storeys
Roof shape: symmetrical gable
Style: open
Orientation
Maximum heights/limitations
Further requirements

[U]Anforderungen der Bauherren[/U]

Style, roof shape, building type
Basement, storeys: yes, 2
Number of people, ages: 6, 40-35-12-9-7-5
Space requirements on ground floor, upper floor
Office: family use or home office?: family use
Guest bedrooms per year
Open or closed architecture: open
Conservative or modern construction: doesn’t matter
Open kitchen, cooking island: doesn’t matter
Number of dining seats: 8
Fireplace: yes
Music/stereo wall: yes
Balcony, roof terrace: yes
Garage, carport: yes
Utility garden, greenhouse: yes
Other wishes/special features/daily routine, also reasons why this or that should not be: space for the family, master bedroom can be small, granny flat will be rented out, exposed roof structure

[U]Hausentwurf[/U]

Who designed the plan: Architect
- Planner of a construction company
- Architect
- Do-it-yourself
What do you particularly like? Why?
What do you not like? Why? TV area on the ground floor
Price estimate according to architect/planner: €450,000
Personal price limit for the house, incl. equipment: €420,000
Favored heating technology: air-to-water heat pump + photovoltaic

[U]Wenn Ihr verzichten müsst,[/U]

On which details/extensions
- you can do without: upper floor master bedroom can be smaller
- you cannot do without: each child having their own room

[U]Warum ist der Entwurf so geworden, wie er jetzt ist? [/U]

E.g.
Standard design from planner?
Which wishes were implemented by the architect?
A mix of many examples from various magazines... yes
What makes it particularly good or bad in your opinion?

[U]Was ist die wichtigste/grundlegende Frage zum Grundriss in 130 Zeichen zusammengefasst?[/U]
I have read a lot in this forum and mentioned the ideas to the architect. At this point, I would like to sincerely thank everyone for that. I am open to any criticism/arguments.

Attached are the pictures

Is the separate apartment intended as the 4th children's room, otherwise one is still missing?

You can't build the house with your budget...

I'm not sure if you are allowed to build that big. The ancillary facilities are still to be added. can you please take a look at this?

Where is the 4th children's room?
The budget is not sufficient.

Is the granny flat intended as a 4th children's room, otherwise one is still missing?

It is probably the room on the ground floor (utility/sleeping).

Almost 300 sqm area (including living basement) for the desired € 420k including photovoltaic, kitchen, fireplace, and whatever else. Respect! Normally we always calculate with € 2.xxx per sqm living area + basement + ancillary building costs + equipment + garage/outdoor facilities. That doesn’t add up.