Here's the floor plan, unfortunately you can't cut off any part like that.
That's true
You can't cut anything off from the 10.45sqm room and the 40.55sqm is also needed for kitchen/dining/living room...
Too bad. But sometimes the floor plan allows it. At my girlfriend's place, the guest toilet and large bathroom (I even think it was 13 or 14sqm) were arranged right next to each other. In that case, it was possible to extend the guest toilet.
It was just meant as a suggestion...