Floor plan ground floor + upper floor for semi-detached house

Using the garage as a cellar replacement is not (not everywhere?) permitted. There are even court rulings declaring the repurposing of garages by owners as impermissible.

Did you make the plan yourselves? Or is the proposal from a planner?

The floor plan with 7x10m and the arrangement of the staircase come from the general contractor (GU). The arrangement of the rooms is more our idea.
It is clear that the living room is oriented to the south. This automatically results in a similar arrangement.

The first thing I noticed right away:
Why do you need so much traffic and storage space for vehicles?

In the floor plan, the living spaces would be way too small for me and the hallways too large in proportion. In the bedroom, my 18m² already feels almost too tight. A 2m wardrobe for 2 people, that is just never enough; I almost had that alone as a student. Well, you still have the attic and the storage room, but surely you don’t store clothing there? The children’s room might be okay size-wise, the office maybe as well (mine is about 30m², but that is more like a second living room for hobbies, etc.).
Also, 23m² for the living and dining room? I think it will be a bit tight with dining table and sofa, etc. Then the kitchen with only 8m². That might work if no table has to go in. Still rather dark, even if the carport has a glass roof. Maybe you can cleverly redistribute a few square meters from the hallway to the rooms?
If possible, I would still build somewhat bigger and waste a bit less space on parking spots. As far as I can see, access to the garden can only be through the garage. Or do you also have access from the south side? You might want to keep that in mind when designing the garden, because it will be difficult to get heavy equipment and materials in later on.

I would also like to make the hallway smaller, but how? The bedroom is sufficient for us. A 2m wardrobe is enough. Originally this was included in the office.
We simply don’t have 200sqm of living space and don’t need it either. The size of the rooms is sufficient, only the arrangement is poor.
Building larger means additional costs and our budget is already almost exhausted. We simply don’t want to build bigger, higher, and more expensive.
I don’t see it as wasting space for parking spots. It can hardly be wider, because then the driveway would be narrower. Getting in and out of the car would be annoying. We might have to build with a different general contractor after all so that it doesn’t become disproportionately more expensive when leaving the 7x10m grid.
The garden access will definitely be blocked. That’s usually the case with a semi-detached house.

Using the garage as a basement replacement is not (not everywhere?) permitted. There are even court rulings that declare the repurposing of the garage by owners as impermissible.

As long as no one objects, there are no problems. The building authority will probably ask why the garage is so small and what we want to "park" in it.

Basically, it must be said that the size of the rooms is sufficiently large for us. More space just costs more money and why should I get into more debt if I don’t need it later? We have chosen to live as centrally as possible, and the price per square meter is simply very expensive there. We would rather invest more in equipment. What good is a 50sqm living room or a 20sqm bedroom to me? Of course, if I get it for free, I’ll gladly take it. But at an average price of about 1600 EUR per square meter, every unnecessary sqm is just too expensive for me.

Your comments are all valid, still depending on personal taste. And nowadays the majority always wants the maximum, not the minimum! I feel good when the house is paid off in 20 years with a low rate.

So if anyone has ideas on how we can make the hallway smaller and brighter to create more living space ... bring them on, I’m all "ears".

The bathroom itself is sufficiently sized. But the T doesn’t work.
Try arranging the floor plan with furniture.
Our TV corner is now 4x3.70. Yes, it works – but for us it’s only the TV corner. If I imagine the room being about 2 meters longer and also needing a dining table in there. Oh dear.
Regarding the stairs: Normally the walking width is 1 meter. With a half-turned staircase you would need a width of AT LEAST 2x2.25. The way your stairs look, they barely have a walking width of 0.80cm. For a house, that’s a no-go – as a space-saving staircase for the attic or in a maisonette apartment – okay.
About the utility room: You want an air source heat pump. Indoor or outdoor installation? Depending on that, you need space inside for the fans. Water connections, electrical connections (large fuse box and probably a separate meter for the heat pump), telecom connections, all that already needs space. Then add dryer, washing machine, possibly a second refrigerator or freezer, laundry basket, beverage crates, brooms, vacuum cleaner, possibly a small shelf for knick-knacks that should be quickly accessible, like toilet paper, shopping basket, supplies.....
In our house, we planned a separate technical room, a storage room, and a utility room over 12m2.
What do you want to do with that 1m wide niche in the utility room? Dryer and washing machine don’t fit side by side crosswise. They fit lengthwise, but then nobody can load or unload laundry anymore, because at 0.40cm no one can stand in front anymore and still open the door.
Your bedroom. Around the bed there’s still a walking space of 0.60-0.80. Enough to walk, but comfortable is something else, not to mention if you ever need help or crutches, then it won’t work anymore.
Depending on how old your child is, you still need space for stroller, baby car seat, muddy clothes, etc. If the child is older, of course you don’t need that space anymore.
Honestly: if the room sizes are okay for you, then you are better off with a condominium. You don’t lose so much space to hallways and stairs.
If you basically want to keep the floor plan as it is, then make the door face forward, where you planned the parking space. Then you could put a functional utility room next to the kitchen. On the left you would have space for a technical room or you enlarge the stairs. For the wardrobe, I would only make a niche instead of a separate room.

And the staircase will be a spiral staircase? That is measured very tightly (and steeply).

Your comments are all valid, still depending on personal taste. And nowadays, the majority always wants the maximum and not the minimum! I have a good feeling when the house is paid off in 20 years with a low rate.

So if anyone has ideas on how we can make the hallway smaller and brighter to create more living space ... bring them on, I'm all "ears"

I think it's okay when you say: better small and mine, than big and too expensive. You can also be happy with smaller living areas. I do need more air and space around me as well, yet I am occasionally surprised by the circumstances when people say "I need over 200 sqm, we are 4 people."

Now to your semi-detached house: You should get the maximum out of your minimal space. You have a nice southwest location, something should be done with that. Say goodbye to a huge hallway and limit yourself to a vestibule/coatroom. With one child and no basement, you can design the staircase open, e.g. in the dining area; it doesn't need a connection to a hallway! In the bathroom, you can do without the T configuration; a simple arrangement of the sanitary fixtures appears more elegant and larger than additional walls in the bathroom.

I would be interested in the floor plan from the builder!

A small addition to YPG, either you set a measure of space and try to get the maximum benefit from it, or you set the benefit and try to minimize the space. Getting the maximum benefit from a minimal area is not possible. You have to limit one of the two factors, otherwise the calculation won't work and you'll get confused.