Floor plan optimization city villa + fill consideration

Ok, I'll skip the 10.8x10.8m. That's a lot more money for nothing. No gain.

What does bd/dd 20/20 mean?
Do I then have a 0.2m×0.2m protrusion? Like, for example, in the wardrobe or the parents' shower? So I can't place a closet as originally drawn there, and there's such a protrusion in the shower?

Floor penetration/ceiling penetration 20x20cm

BD/DD= floor penetration/ceiling penetration In the shower there is only a floor penetration, therefore no projection. In the dressing room the soil pipe is ventilated (via roof), so there is already a projection here. It could not be integrated into the WC's pre-wall because otherwise it would be in front of the guest room window on the ground floor, I assume. Whether the ventilation could be routed as secondary ventilation into the pre-wall so you could at least save the shaft in the dressing room, I don’t know. There will also be a shaft in the living room. Edith says I was too late.

What does bd/dd 20/20 mean? Do I then have a 0.2m×0.2m protrusion? For example, in the parents' wardrobe or shower? So I can't put a cupboard there as actually drawn, and there is such a protrusion in the shower?

No idea - just tell me the post number of the plan you are asking about. The abbreviations have already been explained, but what consequences they have can only be speculated from the specific plan. On the one hand, they can be harmless penetrations of controlled ventilation ducts or the like - so something you wouldn't notice anymore on the finished floor - but also things that affect the room itself. Especially if BD and DD are stacked in the same room, you can read the 20/20 cross-section as a strong indication that they will be connected to a soil pipe. This is a consequence of the energy saving ordinance, no longer chasing soil pipes through exterior walls. Where cupboards are supposed to stand, you should almost always "see red" where such things are drawn. With today's generous group showers, "walk in" does not immediately turn into "vade retro" if a pipe is boxed in in a corner at the back - for symmetry dogmatists, of course, it's a total disaster: then the chakra of the mixer tap sits crooked *LOL*

Thank you.
Here are the current plans.
Can you speculate on what it might look like visually?
And how it could be done better?

I want to be able to place my cabinets in the walk-in closet.
What is that supposed to be on the kitchen peninsula? There is a symbol without a label.
And I don’t like that in the living room next to the couch either. It takes away 20cm of sofa space, and visually I actually don’t want that little piece of wall there.

Well, that's how it is. The downpipe from the children's bathroom comes down next to the sofa. If the wall stub there is not a lintel – which means that living/dining areas flow into each other without division – this downpipe could be routed into the wall of Child 2. The downpipe for the shower/washbasins of the master bathroom comes down next to the cabinet in the guest room, and from the dressing room to the head of the guest bed there is probably a downpipe for the WC in the master bathroom. The sink also needs a drain; you have to imagine "DD" written there. Such drywall blemishes are the price for "social villa construction" with walls that are not aligned vertically. This is almost unavoidable if you want to plan "cash" "private" in this format.
Anyone who wants to avoid this must be willing in this segment to adopt functional standard layouts or be able to think (or learn to think) "in structural engineering and supply and disposal technology" instead of in rosy Pinterest pattern house pictures.