Single-family house approx. 160 sqm flat roof - Optimization / Planning

It should definitely be a prefabricated house, but I will inquire accordingly about what it would mean in terms of cost. If there is indeed more space upstairs, some "problems" upstairs would be solved (size of the utility room and dressing room). Unfortunately, the heating cannot go upstairs due to the energy supplier (district heating), which we had also considered. Does anyone have a brilliant idea, maybe with a half-landing staircase for the ground floor for the rooms: guest room, technical room, guest WC, cloakroom? I had already considered, to make the cloakroom bigger, possibly making the access to the technical room "through the stairs," if possible.

preferably a double garage with storage/hobby room

I've put such a wreck on your property. I think it's suboptimal. Let's see what the others have to say:

I can't really imagine the upper floor setback either. But maybe it's not so bad once the elevation is available.

Also suboptimal, especially since the floor plan doesn't wow me either. On one side there are narrow spots and on the other a lot of empty space.

From the dining table straight to the guest toilet! Is that really what you want?

No one needs that. No guest wants to leave noises or smells there, no overnight guest wants to go through the kitchen to the toilet or past someone showering at the breakfast table.

That means I have to carry the laundry back down anyway, sometimes wet. That then doesn’t make much sense anymore. Just a thought.

Thought for you: Dryer next to the washing machine and TV in the bedroom.

The offset probably costs you only minimally or not at all less than if you "run through" right away.

Attention: Observe the floor-area ratio.

Had already considered making the access to the utility room possibly "through the stairs" to enlarge the cloakroom, if possible.

The area is not "optimally" solved. I would be grateful for creative ideas.

Just discard a failed idea, clean your own hard drive, and get a new approach from somewhere—I'd commission an architect who earns good money. You’re still at the beginning anyway... play around, but don’t lock yourselves in!

I do not want to iron in my bedroom. Of course, there is a TV there, but the bedroom is my bedroom. For reasons of child supervision alone, the living room is more suitable.

Do not iron at all