Divide room later

Even the door situation becomes tricky.

with closed windows about 2cm wide where a wall could be docked.

On this sandbank, I don't see the desire to anchor.

Correct, all the assumptions were right,

Finally, I have already been accused here several times of wild speculating ;-)

Is the house already standing or do you want a floor plan change for a new build?
I guess I'm not the only one assuming it's an existing building...

Regards, Yvonne