Floor plan design single-family house 150 sqm - tips for improvement?

And the balcony has things of a winter garden,

I can't imagine that the winter garden doesn't count for the number of floors. Just like the sauna. So much for that. The fact that "one" doesn't want to admit that only underlines the questionable nature of the roof terrace.

Who cares about the number of floors after five years. First, a roof goes on top. Then a bit is saved again, then side elements are added. It's done.

Ha, only you believe that. The neighbors all have to build single-story. The one next door with the bungalow is already complaining about the carport. If something else gets added on top now, he will immediately ask how and why that is possible.

It is located on the slope. Right? He is building into the slope? So he is building a single-story with a basement, only the basement will have doors and windows on one side because of the slope, but the roof garden is part of the ground floor and nothing on top, I hope I understand the plans correctly. Doing it this way is the most cost-effective option in this special case. Without a basement and instead a larger bungalow, due to the earthworks, it would be uneconomical in my opinion. Also, one should maintain the natural terrain profile as much as possible. That way you protect yourself and others best from heavy rain problems. Karsten

Just a stupid question, because I have no clue about this... Is it clear that the basement counts as a full floor? It's on a slope. What are the regulations there?

He probably planned it so that it counts as a basement. Because the height of the floor is on average less than 140 cm above ground level.