Single-family house 150 sqm basement with 15 sqm upper floor in the outdoor area

I would place the front door centrally between the wardrobe and the stairs. The 1.5m is too narrow, and if you remove it from there, you can also use that side for additional cabinets, hooks, etc. The 2.7m in the shower is huge! The problem may arise that despite warm water, it always feels cold because the heat dissipates through the large shower space.

Planning involves more than just randomly arranging rooms. Factors such as structural integrity, utility lines, and aesthetics all play a role. It can happen that at certain critical points, situations arise due to the interior walls that you simply don't see beforehand with your "approach." After all, you don't plan a vacation without knowing when you have time.
I have pointed out three times now that planning without walls makes no sense; other users have also given you this advice. Whether you take it is up to you.
I'm finding this a bit silly now. Sorry.

I meant the installation in the attic. You have the gallery there anyway. As long as the stairs are not an obstacle to good music enjoyment.

So I would like to have it in the living room, since that’s where it will be used.

I have quite a bit of handwashing.

We hardly have any at all.

The dryer is also emptied and cleaned at the sink.

The condensate runs into that drain.

For me, the way you plan it would be an emergency solution.

I guess it also depends on life circumstances. But I can fully understand that.

I would place the front door centrally between the cloakroom and the staircase.

That would look nicer, but I want the entrance area to be separated by a door.
Between the stairs and the kitchen, you could put a glass door, but it offers hardly any sound insulation.
From our experience, front doors are always the weakest point.

The 2.7m in the shower is huge! The problem can arise that despite warm water it always feels cold because the heat dissipates in the large shower room.

Absolutely right. But we now also have such a big shower and manage well with it.