Sound insulation - house is very noisy!

There are special soundproofing boards from Isover.

ISOVER Akustic SSP 2 sound absorption board

Does anyone here have any experience with them?

I have to tell you unfortunately in a solid house with unfilled bricks this is normal up to a certain degree. You have a lot of cavities in every wall...

That's why this is about "damage control" ...

we (unfortunately) also have something similar (just not as severe). The idea with the partition wall would be something. If possible, try to rearrange heavy furniture (against the walls) and use sound-absorbing materials, e.g. heavy curtains on the windows.

Otherwise, consult experts. Or maybe consider swapping rooms. Of course, this only helps if a room acts as a "sound buffer" in between.

How is the ceiling structure?

My daughter's room is adjacent to our bedroom. She has a large gable in the room.

Could it be that both rooms share one and the same "gable"?
*) this week I am too tired to decline the roof-thing glossary again