Single-family house with 190 sqm - What do you think about the design? Feedback?

Actually, it only needs to be explained that the basement is not really a basement, but rather a lower ground floor, then the next one is called the upper floor (OG), which goes on top. It can then remain at 2 stories. It can, but it may also be better to go down to the third basement level. It’s all a question of the property. However, this needs to be planned accordingly, since the rear area built into the ground gets few windows. If you don’t understand something, you have to ask, but you shouldn’t ignore what you don’t like or don’t understand. Just as we asked without receiving an answer, about how much slope or inclination there is in the building window.

the problem is that we have a fully furnished apartment of the size, but it is laid out completely differently

And that is not a problem. Everyone who builds accepts changes and currently lives in an apartment or house with furniture. You don’t build a house around furniture, you build a well-thought-out house that is easy to furnish.

To be honest, I find this more helpful than the aggressive "the budget doesn't fit at the beginning" comment. The building area is 15*15m and the slope runs relatively diagonally through it with about 1.5m difference from the bottom left to the top right, with the access road coming from the top left. How much more expensive is it if you have to raise it? You would have to level the diagonal anyway for the access road.

A slope that diagonally runs through a building envelope, approximately half a story in height, calls for an architect experienced with slopes. Proceed as I have described.

If you show up with your own preliminary draft, you are putting on a corset. Not advisable. Terrain, zoning plan, your room program, possibly a soil survey. And then let the people work first.

Such a design could also be discussed here much more effectively.

A question about the topic of basement and garage. Can a garage simply be integrated into the basement or are there problems or specific things that need to be considered? Does something like this cost significantly more or is it worth it compared to the saved costs for the external garage?

That is of course possible and is often used for hillside properties. The ceiling must be insulated evenly. If the access is from the valley side, I would seriously consider it.