Optimization of floor plan and bathroom planning with sloped roof

No, it doesn't work that easily. You have rough construction dimensions. Additionally, a bathtub should not be set tightly, just like the washbasin. So if you're unlucky, you'll only have 68 cm left of the 76 cm. That is not functional. I also wouldn't place a washbasin directly in front of a window, because then you might not be able to open it at all.

Where is the downpipe planned on the ground floor?

I think you should proceed as follows: 1. have the draftsman create a correct set of drawings (if the 230 line were the only error here, it would be Christmas and Sunday today); then show us 2. the entire attic floor (not just a section), 3. for context very importantly also the entire ground floor and 3. a gable-parallel section. In the meantime, look at the example of the Town & Country Flair 113 to see how a construction proposal of this type looks as a bestseller.

I notice row after row of botches and peculiarities here, without any claim to completeness and listed below in no particular order of importance. There are statically questionable central purlins drawn in, which according to their position in the floor plan are arranged above the lintels of the gable windows. These windows are supposed to be 1.70 m high starting from a sill height of 94.5 cm – according to Eva Zwerg, the lintels therefore begin at a height of 264.5 cm. Even if there are no roller shutter boxes on top, the bottom edges of the central purlins can hardly be significantly below 290, and thus probably above the attic floor ceiling. What the hell is then the informative value of drawing the purlins in the attic floor plan? – that would only exist if the purlins as beams limited the room height. At least the window height indication is probably wrong. But even at a height of 1.30 m, the gable windows would be very unsuitable for shutterlessness (or for external roller shutters). According to the drawing, the bathtub drain will lie above the stopper – I would summarize that under “hostile user comfort.” In the shower, the fitting will probably come from the drywall (i.e., from the side), and for storage you have to bend in front of the slope. The draftsman should write an essay on how he imagines transporting things between the attic and the ground floor – that will certainly be funny to read. One should not become a draftsman with this level of spatial imagination – is this floor plan an AI fake?

The drawings of your improvement efforts are easier to discuss if you orient them like the original.

Where is the downpipe planned on the ground floor?

.. and how high is the knee wall?

.. and how high is the knee wall?

The knee wall is probably 33 cm here (with Flair it is 76 cm in the standard). But I think the draftsman hasn't even asked the AI the question about the section yet ;-)

Just quickly. Shower then with a frosted glass wall. Shower 90 by 140 is definitely large enough.

Hello Your answer somewhat misses the point. The question is not what the draftsman did wrong. It is to be assumed that the children's room window should have the same sill height. The question to the OP is what is wrong now? Sill height or window height. In my suggestion, any sill height is acceptable.