Ground floor approx. 100 sqm, upper floor expandable (planned bathroom, 2 children's rooms, 1 storage room)

My impression of the attic and stair layout is that the drawings of the ground floor and attic are most likely simply oriented in opposite directions.

The original poster has explained this to themselves or the drawings (where south is located on the ground and upper floors)

Your house would absolutely not be mine, but it does not have such gross and fundamental planning errors as this one.

Sigh... Climbee is so often right. It is what it is. I see an attic that will become cozy. The windows go up to the ceiling, but the windows are not extra tall; rather, the beams are very low. They press down from above. The slopes now offer a bit of a cave effect, but can be oppressive when living there. I would be careful with the conversion to not develop too many rooms there. Otherwise, it will become too cramped!

The staircase in this "sketch" also seems to be exaggerated by 30cm to me, or how long is it exactly?

One wonders how far the construction has progressed. Has the staircase already been ordered and completed? How far along is the ceiling exactly? Is the staircase opening already history? Are the door openings still adjustable?

When you hear that almost everything would have been allowed, it makes your toenails curl. You would most like to replace the staircase and raise the roof with a knee wall of 1.25m. But unfortunately, this is no longer a 3D planning game.

But everything is already down there. Living room bathroom, kitchen, utility room, bedroom, children's room. Later upstairs there will at most be an ironing room and a second children's room or guest room. And you can always fit that in there! Always. About the beams... I'll just make a ceiling where they're visible. Looks nice too... And misplanning. Dear ladies, you sometimes turn into hyenas when things don’t go your way. The house is almost finished, it is simply rude to tell someone here that what’s being built is all rubbish. Then silence would be better if I don't want to praise. Guess how often I just stay silent in the house pictures thread. Karsten

Ideally, you would replace the stairs and raise the roof with a knee wall of 1.25m. But unfortunately, that is no longer a 3D planning game.

I see it differently. Why the knee wall? It was supposed to be a small living unit where later the child would get a finished room upstairs in the attic. There was never talk of a complete rebuild because it was meant to become a fully functional "1.5-story house." But I agree with you: with a bit of common sense and occasional 20cm buffer or extension (concerns the mentioned walking surface, wall stub, width, and heights), everything would work better. But that is all thoroughly discussed.

Later at most the ironing room and second children's room or guest room upstairs.

Please read. The original poster wants 2 children's rooms, a bedroom, a bathroom and a storage room upstairs. It is clear that this is no longer possible now. And it is also clear that he can live with less. But anyone who is resistant to advice should not be surprised when reality catches up with them.

What I find even more striking is what the general contractor or architect (can you still call them that?) delivers here. Built as ordered – not a shred of common sense is invested nor is the customer ever advised.

You just have to look at or imagine a few situations. You’re carrying food into the living room, the child comes out of the bathroom/toilet... -> the result is that everything ends up on the floor and you have to cook again. Similar situation when you want to go from the living room to the bedroom, you pull the door towards you and then somehow have to crawl under the stairs to get in there at all.

The mini kids’ room is completely useless and I say that as a father of three children. The kids sleep in the bedroom at first anyway, well, wait, you don’t even have room for a bedside crib with you...

In my opinion, this is just a total mess, sorry.