City villa floor plan 150 sqm - improvement suggestions

This design is bursting with spaciousness in the living area (area between dining area and seating corner), upper hallway (due to the positioning of the straight staircase), dressing room (due to the parallel corridors) and bathroom (due to the excessive length) without offering any apparent benefit. I would not build like this and the suggested changes would result in a completely different house.

That is a good point. I will improve this once again. How wide should the "path" into the room be at least (currently it is about 1.00m)? What alternative is there for the dressing room?

Just make an L with the cabinets. But it is like this: first relax the living area, the kitchen, the dining area, etc., then something quite different will emerge.

Is your TV really as small as shown?

I'm backing up a bit and adding some screenshots. Everything works fine. I adjusted the sofa (the seating area also plays a role; the current one is 2.70 x 2.70). Whether it should be that way, with the master bedroom facing south, which is gigantic compared to the 12,x children's rooms, is up to you. The bedroom is over 26 sqm, the bathroom about 11 sqm. Interior walls are only 10 cm and above the lower ones. Realistically, the children's rooms will then be about 11,x sqm.

Thank you very much for the screenshots. I have currently assumed all interior walls to be 17.5cm thick in RoomSketcher. After a look at the construction service description from Roth, I noticed that all non-load-bearing interior walls are executed with a thickness of 11.5cm and all load-bearing interior walls with 17.5cm. I have now adjusted that. I am surprised that the dining table in the ground floor suddenly fits with you after all. I have now placed it more in the room – assumed necessary width of 2.80 (1m table + 2*60cm chairs + 2*30cm clearance behind each chair). How do you arrive at the values of the bedroom and children's rooms? After adjusting the wall thickness, I come to 7.6sqm dressing room, 13.6sqm bedroom, and 13.5sqm children's rooms each...

I have currently assumed all interior walls to be 17.5cm thick in RoomSketcher. After looking into the construction service specification from Roth, I found that all non-load-bearing interior walls are to be built with a thickness of 11.5cm and all load-bearing interior walls with 17.5cm. I have now adjusted that.

As a layperson, you can’t go wrong by assuming the "load-bearing" wall thickness everywhere "to be on the safe side"—for the 6 cm difference, you can at least buy yourself an ice cream anyway: if this decided anything about furnishing possibilities at any point, the planning would have been flawed anyway.