How to change the floor plan?

Accordingly, you could adjust the staircase and eliminate this corner at the entrance.

With your shower/stair proposal, it would be no problem to no longer get a long ladder up.

Best regards in brief

I wouldn't have thought that anyone would come up with concrete suggestions again.

The suggestions were already concrete by the pages, you just have to be able and willing to read. Not all participants can magically produce in drawn form right away what they mean.

As it is now, my wife wouldn't go along with it, because the bathroom becomes too small. (She wants to put the washing machine and dryer in there, for whatever reason...)

A bathroom-laundry room combination in a bedroom wing à la honeymoon suite. No further questions, Your Honor.

The ground floor is to remain as it is, that's certain.

That is a bad premise – not to say: too heavy a burden – for the simultaneous call for suggestions for improvement. The ground floor also sets the framework for the upper floor, from which you can only break out at the cost of cantilevers or setbacks. In this respect, it "bears responsibility" for the designability of everything else.

Take a look at the building envelope and tell me what could have been done better. You’re almost forced to build with angles.

One could have also used the possibility that the flat roof allows more freedom for non-parallel eaves sides.

With your shower/stairs suggestion, it would be impossible to get a long ladder up anymore

So I really thought for a full 5 minutes about what you mean. No idea - the head clearance shouldn’t change. We’re only extending the outlet and cutting something off the curve at the bottom. Are you sure?

As it is now, my wife wouldn't go along with it because the bathroom would become too small. (She wants to put a washing machine and dryer in there, for whatever reason...)

...as if that wasn't enough! I give up.

However, if I rotate the bedroom and bathroom, it might work.

It's not that simple. Then you would have the drains in the living room and the view of the garden from the bed would be lost.

One could also have used the possibility that the flat roof allows more freedom for non-parallel eave sides.

Honestly, I don’t understand a thing.

..also that on top of everything! I give up.

That's just how it is when you build together

The only condition I had was a hobby room and then my wife came with her ideas...
3 children's rooms, guest room, bathroom with space for a dryer, windows everywhere if possible.

The size of the children's rooms wasn't my idea. I could have lived with just 5 rooms.
In a pinch, you can also put a guest in a children's room.
The kids just have to sleep too far apart in one room sometimes.

It's not that easy. Then you'd have the drains in the living room and the view from the bed to the garden would be lost.

There would still be a view of the garden. The garden basically faces east, the terrace still has to be drawn in.