You posted this on an American website, so we don't deal in meters or know what a schlafzimmer is without looking that up. We also live a bit differently, so you might want to post this on Houzz.uk instead.

That said, I can't tell from your drawing, but if you don't already have a wall-hung toilet, then I suggest that you switch to one of those instead (maybe Europe only has wall hung toilets). That move will free up space in a small bathroom for you.

I remodeled a house that had an existing bathroom like that years ago. My client called it the "flu bathroom" because you could sit there to take care of one symptom of the flu while at the same time take care of another symptom of the flu in the sink directly in front of you. We made the bathroom larger.

It is a very tight space. Perhaps you could use part of the closet north of the bathroom and put your vanity in that space with a closet in the leftover space. The vanity would be in the open hallway between the bedrooms.

Then the room below could be a shower with a toilet and maybe a very small washbowl just for the toilet.

It's like a camper or tiny house.

That's fine if one

- beautifies, elsewhere;

- is not a glutton for stuff;

- um... skinny & short..er.

I'd use a shower curtain, for elbow room

It will be interesting to see what someone else comes up with.

I'd add another floor or loft for sleeping. and that area for a bathroom, beauty room, laundry, and linens, etc...