Poor layout of a 4.5 sqm ground floor bathroom with shower

To what extent is the window a problem? Because water condenses there?

I have now measured in our apartment. We do not have a shower cabin here, only a bathtub with a partition. The distance to the wall is only 71 cm, and with my 187 cm I have had no problems so far. I think 80 cm on the short side is okay as a second shower.

And, can the bathroom door be moved?

Ah sorry, I overlooked that! Hardly, then the start of the stairs comes. Only a few cm, and also not preferred, because another door is directly opposite, and thus an offset would be visible.