Thank you very much for your answers and tips!
I spoke again with the planner. We can make the facing shell consistently 22 cm instead of 25 cm. Then I would do the same at the washbasin to avoid the offset. Since the washbasin would then protrude 7 cm further and the bathroom is already quite small in reality, I will probably make the door open outwards. That way, you have a greater sense of space in the bathroom.
I am now considering whether to make the shower with a straight back wall and a glass panel oriented at 90° to it, like on the left in the picture. Or on the right as originally planned, where the facing shell continues at an angle and the glass panel is oriented at 90° to that. It would be somewhat unusual but, as already mentioned, it also has a certain charm. However, it could also cause more splashing water at the entrance to the shower.
