Floor plan 2 full floors KFW 55, 136 sqm flat roof

I myself also only had a 10 sqm own room before in a shared apartment facing northeast. That’s fine for our kids. I think our son will play a lot with us on the ground floor in the first years.

I myself only had 10 sqm of my own room back in the day in a multi-family apartment facing northeast. That's fine for our kids. I think our son will play a lot with us on the ground floor in the first years.

I would also shift the entire building 0.5 - 1.0m to the left/west. Although it then stands exactly on the eastern 3m line, the driveway with carport and entrance situation is very cramped. On the other hand, there is 9m of plot depth on the west side, so you can take some space away there with a clear conscience. You will need an oversized carport with storage anyway. Planning everything with minimum dimensions will not work.

We have a very similar house size, but somehow it feels very cramped with you... This is probably largely due to the staircase.
However, I would reconsider it not just for this reason. Are you sure you want future visits from your children to have to walk through your living area every time? Personally, I like my peace in the evening, in my pajamas on the sofa, that staircase would drive me crazy.
I like the bay window idea, I might even do it like that in hindsight, but it still feels very tight with you.
The upstairs hallway is way too big in comparison, which again is because of the staircase.
Unfortunately, your cloakroom won't work like that either, it is far too small.

What type of stairs do you have? We are considering switching to quarter-turn stairs, straight ascent turning upwards...
Thanks, yes the seating window has to be there... In everyday life a table with 4/6 chairs takes up a lot of space, as we are currently seeing in our apartment.
So in my opinion, most of the time one will be alone or with family in the house. If a few times a year there are visitors in the evening who want to go upstairs, we can manage that.