A large space concept is looking for ideas

Doesn't this huge hallway upstairs bother you? Now you have 4 small rooms, no space for a wardrobe in the bedroom. And if the children move to the basement someday, there won't be a spacious parents' area either.
Ground floor: door from the WC to the hallway, otherwise the guest stands right by the dining table when coming from the toilet.
Door of the pantry possibly to the side? It makes it a bit more inconvenient, but it gives you the possibility to extend the countertop by one meter.

Why do you insist on these external dimensions?
On top of that, you have to dig the bay window in the basement into the ground = costs
The bathroom light well is located in the terrace, even under the door of the dining area
Draw realistic furniture to scale in every room.
Cloakroom missing
Too much hallway
Pantry too small for freezer
Where is the 2-meter line in the attic?

I currently have to assume some exterior dimensions, right? Therefore, let's keep it roughly like this for now. Or what is the best way to proceed? Should I just make up the measurements?

We would like to build with a bay window, but it does not have to be implemented in the basement. So far, we have been told that a cantilever slab causes similar costs as the basement in this area. Therefore, we have continued to plan it this way.
The terrace will not be located above the light well, but to the right of the house. Since this is only the rough plan for now, I have left it as it is.

I currently lack an idea for a reasonable solution on the upper floor with the hallway. Maybe someone else has one.

You have to slim down for your budget. Bay windows cost money. No, you don't have to stubbornly stick to external dimensions. External dimensions often result from the sensible arrangement of rooms. You have no cloakroom, reserve space for 3 bathrooms, think about What if and forget about the now, always leave the same staircase. Break free from that corset and plan with graph paper, a ruler, and a pencil. Move things around, play with it. Leaf through catalogs from big general contractors. No idea how often the shape of our house changed from the outside, with almost the same square meter number, with a consistent room concept. Even the location on the plot was moved several times. That is normal. You have to find the optimum for yourself for your budget, for now. With a sloping roof, you have one, always plan the upper floor with a 2-meter line. Kitchen on the left – terrace on the right, I would swap that. Terrace, garden is the second living space in the summer months. That's where you eat, play, chat. Always the sand dunes through the living room into the kitchen. Stay open to changes. Do you really need 2 offices or can you work staggered so that 1 is enough. Honestly, we have worked partially from home now for how many, 12 weeks, and even one table was enough for us. How much fitness do you still get from house, garden, children. A house takes much more work than an apartment. Maybe there is a new hobby and you prefer gardening.

Just leave all the tinkering based on an outdated plan and rather do the homework of obtaining more precise measurements and heights of the property.

Just leave all the tinkering based on an outdated plan and rather do your homework to get more precise measurements and heights of the property.

I just can’t do that at the moment, as I already said, because the city is still being a bit difficult about it. Mid-August is probably the earliest they are considering here.

And yes, bay windows cost money. We are aware of that. However, for my partner it is absolutely essential that the knee wall is at least 1.50 m. That is very difficult to achieve when the upper and ground floors have almost the same dimensions and the development plan specifies 1.5 storeys.