Floor plan optimization of a single-family house with a basement on a small plot

That is, I think, permissible

Yes, there could even be three.

stairs and small slide to the garden from there

It also looks much better design-wise than an exterior basement staircase.

Slide? Wheee. Well, the paths would have to be at street level. Terrace even higher. It should then look something like this:




Now you can think about how to add more fill, set stairs or "slides" – although I only know the latter from playgrounds.

It is planned for up to 3 children

Well, the paths would have to be at street level. Terrace even higher.

Yes, exactly. According to the TE floor plan, no large windows are needed towards the street, the area will be completely filled up, as will the terrace and parking space, then nicely designed slopes, a staircase and a slide to the garden, which remains at the original height. This will be great.

This will be great.

Yes, I would build a wine cellar right under the terrace...

According to the TE floor plan, no large windows are needed facing the street, the area will be completely filled up, ...

Please consider: The street side is the "light" side. Windows would be nice there. I am more likely planning to redesign the rooms downstairs. I would probably only fill up the terrace and paths. Put windows in front and back.