Staircase shifted by 10 cm, options?

Hello,

I am building a single-family house with a [GÜ].
After the screed was laid, it was noticed that the staircase is offset by 10 cm.
That means it starts 10 cm too early.
According to the plan, there should be 1.05 m of space in front of the staircase, currently there are 94 cm.
Therefore, the last step at the top is 10 cm lower (according to the plan, the last step would not have been a full step).
The staircase is a single-flight two-stringer staircase. Since the house has a basement, the staircase cannot simply be shortened now, as it would then be hanging in the air.
Are there possibilities to reduce the stair opening? The floor (or basement ceiling) is made of 18 cm concrete (filigree ceiling).
Even during planning, the 1.05 m in front of the staircase felt like a tight spot; I would be glad to get at least one meter here.

Thanks,
Morgenstern

I assume we are talking about

Here are the drafts from provider F:

? - yet I do not quite follow your words. At first it sounds,

According to the plan, there would be 1.05m space in front of the staircase, currently it is 94cm.

as if the staircase begins closer to the outer wall, but then

At the top, therefore, the last step is 10cm lower (according to the plan, the last step would not have been a full step).

rather as if the heights are not correct (?)

rather more like the heights are not correct (?)

The heights are correct. By "10cm lower" I meant a 10cm larger step width. So deep not in the sense of high/low.

The heights are correct. By "10cm deeper" I meant a 10cm larger tread width. So deep not in the sense of high/low.

So what now - the top step is not just a nosing, but has a full tread length, and the bottom one is for shoe size 58?

Yes, so now - the top level is not just an exit, but has the full stage length, and the bottom one is for shoe size 58?

Pictures would be helpful. But you probably won’t be able to change much there. (Except tear it out and redo it once/correctly).

I will upload pictures tonight, I’m currently only on my phone. I’ll try again with a short summary, sorry if I expressed it awkwardly. The plan was a staircase where the top step only has half the tread width (about 15cm instead of 29cm). However, it was executed with almost the full tread width, so the staircase protrudes 10cm too far into the hallway at the bottom. The stair builder simply adapted to the conditions because the stairwell opening was already planned 10cm too large. The staircase design never matched the planned stairwell opening. So the stairwell opening would have to be reduced by 10cm, the metal substructure removed, shortened, and reinstalled.