Floor plan, not a specific single-family house, approximately 200m² with 2 apartments

Your last sentence is completely unnecessary,

on the comment

Take a look at functional floor plans and read through the threads here. Then maybe something will come up that can be discussed...

is the height of ingratitude, because this advice is not unnecessary but accurate, and exemplarily summarizes the turnaround to a goal-oriented approach in a compact way. If someone says at 11:30 pm

I want to see what is (approximately) possible and sensible/would be and what is not, and to gain more experience.

although they only became a member here on the same day at 10:44 pm (and clearly no long reading preceded their registration), then hundreds of opportunities to perceive discussed experiences were missed. After all, the idea

The door (with cutout) also runs into the wall and is basically a lying L, so that the bottom edge of the door would just barely pass over the mattress.

is worthy of a year-in-review right from the start :) By the way, the approach strongly reminds me of by ;-) Suggestions regarding room program creation and the like are indeed correct, but in a popcorn thread actually misplaced. Presenting a site plan oriented to the north is usually helpful – but we don’t even know if there is a north pole on the planet where Cloud Cuckoo Land lies. At least this place does not have a stop of the Lummerländer railway, and exemptions from the state building code can surely be negotiated with the childlike empress ;-) My crystal ball currently does not see any Mrs. Right who sets Thomas straight. So let’s leave it at playing, and too much seriousness is only disturbing there.

I would recommend to the OP to plan right away only with drywall on wooden studs on a finished floor. That way he can relatively easily relocate the walls later if he realizes it doesn’t work after all. Then it’s best not to use screed, but rather a (false) floor on joists like in office construction so that he can reroute the cables in the floor however he wants. Then, apart from a few points, everything can also be changed afterwards. Of course, such a construction method also has many disadvantages and some things might even become more expensive, but that is the catch to swallow.

I can say little about the floor plan itself, but regarding the topic of "separation" of the parents' bedroom, since we have two small children: You won't get any sleep even with a sliding door if your partner is sleeping "next door" with a restless child. The only solution is to move to another room. We decided on a larger bed (180 + 90 cm), so everyone has more space and a quieter night.

One more tip: elbows/heads/knees hitting doors or drywall partitions during a restless night are incredibly loud and often wake someone up...

Toilets directly adjacent to bedrooms are also very loud, especially if the door leads into the sleeping area (pay attention to sound insulation class...).

Perhaps as a space suggestion: in the hallway, you can use white, ceiling-high built-in cabinets for storage, so the dressing room can be eliminated or made smaller.

Maybe should clarify again that he/she does not intend to say "you can keep it" with his/her post. Just realize that a "nicer" statement among 10 "annihilations" does not mean: "great, go ahead". The draft is and remains bad, even with any kind of change rooms. Just the location of the stairs alone means this structure is not a two-family house. There is no point in sugarcoating or justifying anything here. These are ill-considered games. I'm out of here.

It’s not about what criticism you bring up, but how you bring it up. And you can, for example, describe something as "unsuitable/inappropriate" or as "sh...". Although I am pleased and grateful for the critiques, as I said, I have the feeling that some only aimed to put me down. The biggest criticism I received was regarding the partition wall in the bedroom and the "children’s bathroom". For both points, I can also understand the concerns and negative aspects (which existed before), and it is quite possible that I will discard those thoughts as well. I will also make 2 or 3 adjustments to the floor plan presentation. However, regarding the remaining points, I have not heard any convincing arguments so far that seem more sensible to me.

I basically don’t care whether it can ultimately be called a two-family house or not (provided there are no subsidies linked to it). But since the staircase could be blocked off with the sliding door, I see no reason why it couldn’t then be used as 2 separate apartments.

We once had a walk-in closet with a sliding door in the bedroom, which we had custom made by the writer. Because of different waking times, we thought you could calmly pick out your clothes in the morning and get dressed after showering. But the sliding door alone already made noise, despite the running rail on the floor and the damper at the end. It was loudest when it was pulled the last bit to really close. It didn’t help at all; you could hear everything in the closet that you would have heard without it, just somewhat muffled in sound. We could have invested the money for the custom work better elsewhere.

Okay thanks for the experience, noise when moving wouldn’t be the problem now, but that it would hardly mean any noise reduction in the end is of course a point clearly speaking against it. How thick was the door and was it also specially made to be soundproof?

The sound problem with sliding doors is not due to the door leaf. It is because, with most systems, you don't get any sealing pressure of the leaf against a frame. So the door leaf basically floats freely in the track system and only rests on the rollers, and air (and thus sound) can pass all around. Not to mention structure-borne noise... There are special systems for this, but they are immediately four times or more expensive. I also doubt that such systems even exist for ideas like bed separation. Possibly, a heavy theater curtain would absorb more sound than a sliding door.