Minimum distance between washbasin with cabinet and shower cabin

I don't have one yet. It’s currently failing due to the desire for a black toilet seat. I haven’t seen an "affordable" black shower toilet yet. I might possibly get one of those purely add-on seats. If necessary, I’ll paint it black if I don’t find one. Until then, a lot of wet toilet paper helps. Oh, by the way, I’m the advocate for this at our place – my wife isn’t interested.

Are you referring to a suspended ceiling when talking about the light?

No, not necessarily a suspended ceiling, but a square or rectangular light element – of course, you could integrate that more elegantly visually. You can find something like that in the search engine if you look for LED panel.

Our craftsman insists on suspending it "up to the top tile." That would be about 20 cm with tile height of 20 cm and ceiling height of 260 cm.

In the shower area, you can tile up to the ceiling – although from experience, 2.2 m from the shower tray height is sufficient for average-sized people. Opposite the wall, you have no benefit from ceiling-high tiling because there’s no need for water protection there. A plastered wall from a freely definable height (lime plaster is mold-resistant) is perfectly fine – and if necessary, also saves some budget. The room just becomes noticeably more pleasant.
For inspiration, search for 25 English bathroom ideas. Our British friends are very creative. I’ve seen quite a few bathrooms in England with extremely bold wallpaper that gave a very simply equipped bathroom (cost-wise) a downright glamorous touch. If you prefer Italian simplicity, there’s also great inspiration on the web. Unfortunately, the Italian design path often turns out to be quite expensive (Sicis tiles, Tubes radiator, Gi Gambarelli switches, Invisibile door, Boffi fittings and ceramics, Artemide lighting... quickly you have 30k invested in your bathroom without paying a single craftsman hour yet...)

True, but Galja won’t negotiate on that. The bathroom will be used by only one person at a time, i.e., almost exclusively by her.

Definitely fulfill the wish for a separate bidet – for many people, it is essential for well-being. Don’t judge – just do it.

I only know of shower cabins with a fixed element that is half the width of two shower cabin sides, which you then either slide open and closed or fold open and closed. The latter then either only outwards or outwards or inwards.

Take a look around at what is possible nowadays. Regarding the bidet: it depends on what you want to do with the bidet. Bathing feet is difficult in the shower toilet ;) Personally, I would probably put the washbasin at the front, then the toilet (plus bidet), and then a shower along the entire wall with a fixed transparent shower partition. On the right wall from the navel up, a mirror along the entire length, indirectly illuminated with a light strip. Check out Reuter, they also have a magazine with clearances: 20cm left and right of bidet and toilet… between the two, one unit is enough, so it does not have to be doubled. I would try to have the door open outwards.