Flat roof of 170 sqm with a basement on the slope

Garden level and then it gets a mini pseudo-living space

Kitchen and dining in the garden level

Stairs stacked

Remove the air space in the upper floor, proper bathroom upstairs

Maybe a proper split level

There is too much design and too little function here. Mini kitchen Mini bathroom - reminds me of the bathroom in my first 45 sqm apartment

Exactly: the living room doesn’t need garden access. You use it in the evening and sit there in front of the TV. Dining and kitchen with garden access, your upper floor variant is more plausible. And check the ratio of room size to air space. The guest room has a net 8 sqm, but there is a lot of hallway and air for that.

Garden floor and then it gets a mini pseudo-living space

Kitchen and dining in the garden floor

Stairs stacked on top of each other

Remove the void space in the upper floor, proper bathroom upstairs

Possibly a real split level

There is too much design and too little function here. Mini kitchen Mini bathroom - reminds me of the bathroom in my first 45 sqm apartment

Thanks to you too.

I see your points. But can you briefly explain to me again how you would do it in our case or roughly imagine it if the kitchen and dining area end up on the garden floor?

It would have been hard to plan more significantly off the building window. The building window minus two lateral building wedges could make you the envy of all square city villa builders, and you plan the exact opposite: a floor plan that is otherwise only used in village and old town building gaps, whose plots were cut without reallocation procedures. Apart from this rotation of the house axis, this narrowness here only came about because you let the house step back its entire "width" (in terms of its N-S extension) by the terrace depth, instead of at least gaining depth next to it as an "L". This imposes an unfavorable internal layout on the house, which follows its self-imposed longitudinal axis: large traffic areas and therefore long routes, like a towel row house.

At the end of the bowling alley corridor lies a "living room" that cannot decide whether it should be a ridiculous 8 sqm small terrace door forecourt or at the same time a two-story hall. It is neither fish nor fowl, neither dumpling nor pain. If furnished in the drawing, the tiny size would even catch your own attention. The lower half of the living room then also provides access to the utility cellar. You haven’t just been here since yesterday; you really can’t have taken this design seriously. Even if I had vacation this week or were sick, it must have been clear to you that there would have been no paeans.

Follow your plot, prove worthy of its above-average convenient building window for the current market, and don’t unnecessarily twist the building on it. A lot of beautiful things can definitely be developed on it, but for heaven’s sake, don’t take a single jot of this design into the next one – not just the galley, and certainly not the "structure" of arranging rooms as if the house were an extension on row garages.

As a precaution, : let the OP tinker by themselves first.

The building concept is clearly structured and well organized into different living areas. I like it very much - with a few drawbacks that should be fixed.

Upper floor: The variant without an open space in the dining room, with access to the children's rooms via a shared open play area, is my favorite. Building a walk-in closet with wardrobes without inserting a wall is a sensible way to save space. Unfortunately, the bathroom is far too small. If the staircase is moved towards the walk-in closet and the children's rooms are shortened a little bit, space can be created for a slightly larger bathroom.

Ground floor: I think the central kitchen-dining area and the omission of a hallway are great. The wardrobe is out of sight, although a bit small. The study/guest room is tiny and must be furnished very carefully to function. The guest toilet is also very modest in size. You can gain some space by making the kitchen-dining area a bit narrower. With generous window areas, the open space above the dining area is completely dispensable. The division into two living areas is unusual but realistic. I know this from many American houses (which are mostly considerably larger). The upper living area will be used more often during the day.

Garden level: The lower living area is suitable as a retreat and works well with guests when it gets a bit louder. Since all the other lower rooms also have an outdoor access, nothing has to be carried through the lower living room.

I can well imagine living in a house of this kind. Only the study and the wet areas are, in my opinion, too small. Therefore, it is not a house to "grow old in" - but maybe it doesn't have to be.

In the USA, multiple living spaces are common in larger houses.
Here you have mini rooms
Bathroom Kitchen Living Office Cloakroom
Where is a sofa supposed to go?
Retreat with open space on every floor
On the sleeping level, you can hear the TV in the garden room

Garden level
Kitchen Dining Loss of at least 1 cellar room

Ground floor
Living
Leave air space
Guest/workroom larger
Wardrobe larger
Possibly small storage room (to compensate for the loss of the cellar room)

Upper floor
Omit air space
Bathroom reasonably large - it is your family bathroom and 2 people should fit in, as well as towels, hygiene items
Possibly a gallery with play corner later reading corner
or small utility room laundry is done there after all