How to change the floor plan?

And yes, most people only chimed in to discuss supposedly wrong priorities.

I would rather speak of "wrongly prejudged" when the slogan "Change only if it stays the same" is issued, or when one gets caught in the false belief that one can only reasonably follow a polygonal building envelope with right-angled projections.

A fundamental debate about species-appropriate child-rearing would have been dispensable in my opinion, but one of your "discussion assignments" was precisely phrased as:

Would you have an idea how to enlarge the 3 children's rooms on the upper floor without completely throwing the entire floor plan overboard?

and that was in fact done: most suggestions left the arrangement of the rooms untouched and merely tried to reweight the dimensions.

So what are you complaining about, that your wish is being fulfilled?
This is a forum. The advice is free – in return, as "bycatch" one also has to listen to the wardrobe song, the staircase song, and optionally the dressing song or the pantry song. Bonus tracks, so to speak.

and that was done as well: most suggestions left the arrangement of the rooms untouched and only tried to re-balance the dimensions.

So what are you complaining about, that your wish is being fulfilled?
This is a forum. The advice is free – in return, as "bycatch," you also have to listen to the cloakroom song, the staircase song, and optionally the dressing song or the pantry song. Bonus tracks, so to speak.

Well, I can still figure out for myself that the compensation area does not just fall from the sky.

But if the thousandth person tells me the rooms are different sizes, I logically start to feel a bit fooled.

On the other hand, no offense, the drawing by kaho is not rocket science either. What needed to be done was clear: too much space in the hallway and with the parents, too little with the children. Your problem is not the size of the floor area on the upper floor, but the willingness to allocate it differently. No one can carve anything out of thin air here.

...no rocket science...

Yeah, it's almost always fiddling around when you have to twist yourself like that. What bothers me is, why can't the approach be discarded? Has it already cost money? Is the architect threatening to quit everything? Are the bricklayers already going to be on site tomorrow? It's not your brainpower that's being wasted, is it?

Of course it already cost money. We agreed on a fixed price. 1. It currently always takes forever to implement the changes. 2. We have wanted to move out of our apartment for ages. 3. It is a huge effort to plan everything anew because we have to get approval from this damn design advisory board every time. Afterwards we plan something and the board says, no we don't like it. Do something else. This has already happened for the second time and I am fed up with it. Then there's the building time window, which does not allow for easy planning...

Oops, I must have missed something. A design advisory board? What is that? That sounds so socialist - are the Russians coming back now?