Floor plan planning shortly before submitting the building application

The gap on the left would be something with a twist .. maybe even more twist if the diagonal lines ran parallel.

My wife doesn't think the wall is so great, but she would agree. However, she would then also want a wall on top and not a stainless steel railing. There has to be uniformity, she says.

Well, it's just a bare wall. What is there to find appealing about it?

Maybe you'll find some ideas by googling images with "Wandverkleidung+ Treppe".

We ultimately decided against the wall and for a stainless steel railing.

However, after the photo with the stair wall, we are quite enthusiastic about a wooden stair tread. Therefore, we probably will not tile the stairs as initially planned.

Such a look also inspires us, which I found.

If you choose a wooden staircase, have it properly glued.
At friends' place, it was only “underfoamed“ or something like that and started to “creak“ when walking after 1-2 years - really annoying!

In addition, the concrete staircase covered with wood was not exactly cheap
Probably only natural stone is more expensive?

Understood. We of course need to keep an eye on the costs. So far, it was planned to cover the currently scheduled concrete staircase with the tiles that we will also have on the ground floor. In the upper floor, parquet will then be laid.

If we take a wooden staircase, how much does the price roughly differ from the standard scheduled concrete staircase? Is it a big difference?

Wood on concrete stairs doesn’t seem to be a good solution, judging by your statement.