Access to the bathroom only through the bedroom seems impractical to me. I assume that the upper floor is more of a place just for you, without too much visitor traffic.
It will also certainly be the case that you’ll prefer to use the toilet upstairs when longer sessions are planned. Because the toilet downstairs, with its 1.2 m width, just about works, but also, due to the missing window, does not invite you to stay there for long.
And then you don’t want to rush past the bed through the bedroom every time.
The dressing room is too small for me. If you don’t have enough space for it, it’s better to forgo the structural separation and create the partition with furniture. It is so cramped there that the door will probably always remain open, and with the door closed, everything feels cramped so that you wouldn’t want to dress there.
Giving up the wall brings you flexibility and a bit more space.
The further layout of the upper floor is rather awkward, as already noted:
The drainage of the utility room from above runs directly through the living room, conveniently right by the sofa. Then at least you hear it when the machine pumps out and finishes while watching TV.
And also because of the arrangement. It looks as if the upper floor was finished and then a place was still sought for it. That is not clever in this spot.
The extension is a complete stillbirth. You say that just to the north there is a heavily trafficked street. That means that through the windows in the extension not light but only noise comes in. Shoving your guests there is a statement.
As a guest room for occasional overnight stays, it is too large. For longer stays it is also not suitable. It is very expensive space with no real added value. A use case did come to mind, but it is at a regular’s table level and requires a mirror above the bed. ;)
Most of this has already been mentioned, but one thing I do not want to leave uncommented:
We plan pragmatically and practically. It should please us and not become a showpiece for the buddies from the Rotary Club.
This is not pragmatic and practical. The gallery, the extension, the garage, and the shed are luxury.
Especially since 150 sqm is anything but little.
But I don’t find that bad. If you have the budget, then build like that by all means. But be aware that what you have in mind there is rather Rotary than functional building.
Bottom line:
Basically, I don’t think it’s all that wrong and believe that something nice could still be made out of it.
Maybe you let the suggestions from the community flow into a version 2.0 and upload it here again. Then we can deal with it once more. Right now, it doesn’t make sense to give concrete floor plan tips. Too many fundamental decisions and changes still have to be made for that.