Floor plan optimization single-family house, 5 people, 8.5m x 17m, 250 sqm

and what about all the stair railings? The little gates don't help either if a child is clever and old enough... You can also always overdo it with safety

Climb over it? At least I did

The coupling of garage and house ruins many options.

That is practically my main mantra

Unfortunately, I didn't get around to replying during the day today, so just a few sentences before going to sleep.
Thank you first of all for the partly very good tips that help us and also give us something to think about.

1. Regarding the 2 plots of land, unfortunately it is the case that we have access to exactly half of the western plot and cannot purchase the whole thing. This significantly restricts moving the house. I had not described this to you in detail beforehand.
2. I also consider the suggestion of the 3D planning to be very sensible. I think certain things can be assessed much better this way.
3. The location of the staircase complicates things for us, but we have discarded all other staircase variants for various reasons. The variant from could perhaps be an option.
4. The many seats in the kitchen and dining area are definitely not harmonious yet; basically, we will need to scale down a bit in a healthy way.
5. We have hardly any concerns about falling from the gallery. The topic of noise could be more of an issue.
6. The garage in the position with the width obviously restricts us in some respects. Maybe positioning it in the west could actually be an option. Or a narrower garage at the current planned location and an additional single garage in the west. That could make the planning a bit more flexible.

Quite a lot of points. At the moment, I still have no overview of how and what exactly we can implement or use from this. But in any case, many thanks to each and every one who has taken the time to respond to us so far.
Good night.

I hadn’t described this to you exactly in advance.

What a pity. Then it’s only 1200m² left.

Perhaps a position in the west could actually be an option.

Yep, here with mirrored floor plan:
[ATTACH alt="Lageplan3.png" type="full"]47237[/ATTACH]
I left a gap between garage and house so that can put the Q7 and X6 in the garage widened by 1m. Otherwise the house moves that one meter further to the west. For the GRmax=110m² the planner still has to do some convincing work, but with your initial positioning it wouldn’t have been met either. However, now the building boundaries are no longer exceeded; there is even about 90cm leeway. The flat roofs of the dormer and bay window still require an exemption.
Development plan part A, 2.1.2.
Roof structures, roof cutouts and cross gables are permitted with a roof pitch of at least 15°.
The balcony is totally overrated and, as a connecting element between two children’s rooms, bears great potential for conflict and injustice towards the third child. Besides, it costs money and counts towards the floor area. Is there any argument for it?

We have fully glazed our airspace on the upper floor, thereby eliminating all noise and kitchen odor problems without losing the aesthetics. Of course, with your gallery size, that's not exactly cheap. I would also paint the balcony and give Child 3 a wider window. Then everything would be fair. If you have no neighbors to the east but a nice view of the forest, I would put a larger window with a fairly low sill height in the bathroom and place the bathtub in front of it. Then you would have a nice view while bathing, which you currently block with the toilet. I would also give the dressing room a window.