Illuminated partitions in the bathroom

So we also installed that in our shower. I am happy every time I turn on the light and it shines there.

Dry construction or solid construction?

With us, this wall is completely made of drywall.

There would partly be enough space for a drywall pre-wall. But not everywhere... We would reluctantly narrow the shower.

You initially asked about an 11.5 cm wall - dimensionally, I don't see a difference. Which bathroom are we even talking about?

We are talking about this bathroom.

And I would prefer the shower not to be narrower than the 88.5 cm rough construction dimension (if I have to have an additional drywall partition installed for the niche).

I would not equip the wall next to the shower with a [Vorwand], but construct it entirely in drywall. How did you want to cut out a niche in a wall that is only one "head" thick?