Arvivald wrote: I will try it whenever I can buy / borrow a flexible screwdriver
Why do you need a flexible screwdriver? After all, in the first picture you can see on the top screws, which should be unscrewed.
Arvivald wrote: I saw such a view
I do not really know, I can not see much in the picture.
Arvivald wrote: Is it possible to take out the cassette itself (if so)
Everything is possible, it is a matter of technical possibilities. The cassette is pressed / riveted. In addition, it is often ironed into a bolt. I never replace it, always the entire bolt.
Arvivald wrote: after unscrewing the espagnolette from the old window (from which I wanted to transfer the cassette) which has other dimensions so the entire bolt can not be replaced
Each bolt is cut, so if it is longer, but it is in the given range (stamped on it), it can be boldly replaced.
Added after 2 [minutes]: ta_tar wrote: Check at the top if you are able to disconnect the tilt mechanism from the window
Refine.