In this location, the upper left corner can be done with less mirrors than you think.
That is not only stated in the maps, it‘s really, really true.
I just did this location a short time ago myself.
Check the maps very carefully. You have to move some of the mirrors that are already there in this upper left side, to a slightly different position than they are at the start.
Count the mirrors and position them exactly like in the maps.
There is even one mirror left that is not needed.
I assume that you followed the maps to the button for the additional mirrors already.
It would be nice if you could use automatic translation, so other players also know what is going on and can as well learn and help also. As most can understand English (or use automatic translation) that‘s the language we predominantly communicate. It‘s not my native tongue either, but you wouldn’t understand a word, if I helped you in my mother tongue.
@SkoRen : Sorry for posting the direct screenshot for once. Usually I want players to use their ability to tap on a link 😉
In this case, the original setting in the upper left corner looks very similar to the final setting, but isn‘t. For players that are told to compare carefully, but don’t do it extremely precisely, they will still tell you that they have it the same when they haven’t.
One mirror in this „staircase“ of mirrors has to be moved one step down to make it work. That‘s what leaves the other one mirror useless.
I really hope, that it helps now.