Floor plan single-family house approx. 160 sqm - suggestions for improvement?

Hello everyone,

I am new to the forum, but I have been observing for a while and have already gathered quite a bit of knowledge.
Attached are the floor plans of the ground floor and upper floor for a single-family house; I know the dimensions do not yet match the floor area ratio, it is just a rough sketch for now, which I want to improve gradually.

Here are the details:
Development plan/restrictions
Plot size: 500 sqm, rear plot
Slope: No
Site coverage ratio: 0.2 -> 100 sqm
Floor area ratio: 0.3 -> 150 sqm without bathroom on the upper floor
Building window, building line, and boundary: only 3 m distance from the boundary must be maintained
Edge development
Number of parking spaces: 2
Number of stories: 1.5
Roof shape: shed roof
Style: modern
Orientation: southwest
Maximum heights/limits: eaves height max 4.5 m
Other requirements: old development plan -> bathroom upstairs and air space are not included in the floor area ratio; also no sealed surfaces outside

Client requirements
Style, roof shape, building type: massive construction, rather modern, large windows
Basement, floors: no basement, 1.5 stories
Number of people, age: 2 adults, 1 child (3 planned in total)
Space requirements on ground floor, upper floor: see floor plan
Office: family use or home office?: home office for 2-3 days/week
Overnight guests per year: 10
Open or closed architecture: open
Conservative or modern construction: modern
Open kitchen, cooking island: kitchen directly connected to the dining room via sliding door
Number of dining seats: 6
Fireplace: yes
Music/stereo wall: no
Balcony, roof terrace: no
Garage, carport: double carport -> 2 parking spaces as above
Utility garden, greenhouse: no
Other wishes/special features/daily routine, also reasons why something should or should not be: gallery window from ground floor to upper floor -> I know galleries are not very popular here, but we really like this

House design
Who designed the plan: self-made with building brochures and impressions from friends’ houses and show homes

What do you particularly like? Why? Open living area; the center of life and meeting point here; central string staircase
What do you not like? Why? Corridor size on the upper floor; it feels like wasted space because it is really only used as a corridor/hallway to the rooms
Price estimate according to architect/planner: still open
Personal price limit for the house, including equipment: 270,000 € excluding electrical, heating, sanitary, and outdoor facilities -> plot already deducted. We are building in northwest Germany
Preferred heating technology: heat pump

If you have to waive something, which details/extensions
-can you waive:
-can you not waive: size of the dressing room limited by the size of Ikea Pax, gallery window, shower in the ground floor bathroom, roller shutters in the ground floor

Why did the design turn out like it is now?
A mixture of many examples from various magazines...

What is the most important/basic question about the summarized in 130 characters?
I am looking forward to your opinions and would be happy about suggestions for improvement J
I have disregarded windows for now, we are still at the very beginning and it is only about the room layout for now...

Thank you very much in advance for your help and best regards
Karina

added 22.9.: site plan

Floor area ratio: 0.2 -> 100 sqm
Plot ratio: 0.3 -> 150 sqm without bathroom on the upper floor
[...] Number of storeys 1.5
Roof type: mono-pitched roof

I hardly see anything matching here. I don’t understand the subtraction of the bathroom from the plot ratio.

It feels like wasted space because it is really only supposed to be used as a corridor/hallway to the rooms

Still, when "transiting" from one room to another, you don’t like feeling like a pneumatic tube. I can’t quite reconcile saving gallery and hallway space.

A mix of many examples from various magazines...

Rice pudding with dill pickles – stirred, not shaken

11ant, first of all, thank you very much for your reply.

Oh dear, that doesn’t sound very good at first.
The reason for the gallery is that we would like to have a large window spanning two floors as a highlight of the house.

Maybe a quick note on the development plan from 1984 -> old building use ordinance:
Floor area ratio: 0.2 -> 500*0.2=100
Plot ratio: 0.3 -> 500*0.3=150

The number of floors with 1.5 means exactly: one story with a developed attic
A house with a shed roof would fit into the development plan, a few plots away (same development plan) there is a house that is similar to our wishes.
The exclusion of the bathroom as well as the airspace from the plot ratio results from the statement of the man at the building authority, where we have already been to inquire.
The bathroom, which is not located in a full story, is not considered a living space according to the legal situation at that time and is therefore excluded from the plot ratio (which is determined by the external dimensions). The same probably applies to the dressing room (as storage space).

I hope I was able to provide some clarity

Was a semi-detached house mentioned in the initial post? Anyway: Bathroom facing southwest, but the child only gets a few minutes of morning sun in the height of summer? If it is not a semi-detached house, the case is even more serious...

Was a semi-detached house mentioned in the original post? Anyway: bathroom facing southwest, but the child only gets a few minutes of sun in the morning during midsummer? If it is not a semi-detached house, the case is even more serious...

No, it is a detached single-family house and not a semi-detached house.
I have adjusted the north orientation again according to the site plan, I made a mistake there, sorry.
I have uploaded the adjusted files in the original post.
The children's rooms face south and west. Bathroom and master bedroom face north.

The budget and the house do not match. Try to get 4 straight exterior walls. The house is too small for a straight staircase and gallery. There is a lack of storage space – except for the oversized dressing room. Where is the wardrobe for 5 people? Utility room/house technology/storage room too small. Have you ever tried to furnish the kitchen? Remove the door between the utility room and kitchen. It takes up valuable space in the utility room. The kitchen gets a door to the hallway. The staircase looks very small. Upper floor Dressing room almost as big as the children's rooms. Have you already drawn in a bathtub, shower, toilet, and sink in the bathroom? A proper cabinet should also fit for towels and hygiene items for 5 people. Hallway and gallery are space eaters. The two small children's rooms could benefit from a bit more space. What happens to the bay window dining area on the upper floor? Draw proper furnishings in all rooms to scale.