Design for a single-family house with 160-180 sqm - suggestions for improvement?

The headline with 160/180 sqm: does it include the basement? Because I can't see the size anywhere. On the other hand, in my opinion, 160 sqm is not sufficient to decouple the stairs. If it doesn't fit, then the design is not well thought out. A straight staircase with the combination basement stairs can be accommodated within 160 sqm. Furthermore, the living-dining area with 3.80 is too narrow in length: the room is cut disproportionally and will appear very corridor-like.

I wouldn't get too hung up on the narrow living area. You have to zone it cleverly here: different wall designs in both areas, if necessary different lighting concepts. You could make it quite nice. But there is absolutely no need to think further about it, as the floor plan is completely inconsistent.

Current area is 160sqm without the basement. That is actually just a technical garage and storage room. What is completely inconsistent?

What people wrote on the last pages: 2 toilets on the ground floor // separate stairs // unused room on the upper floor but small guest room on the ground floor // doors too narrow // wall thicknesses on the upper floor, especially next to the stairs // window dimensions etc.

On the ground floor, there is no second WC. This is replaced by the wardrobe, and the living room gets a corner there. On the upper floor, all rooms are used - just because it is not called a children's room, it can still be used. That's why the question is whether it makes sense to go up to 180 sqm and thereby enlarge the kitchen and guest room as well as the bathroom on the upper floor.

Stairs on top of each other and you have on the ground floor the extra space for kitchen and guest. What is the corner in the living room for

Landing stairs are just as easy to walk on as straight stairs.