Shower Installation - Experiences, Tips?

So it is due to the fact that sometimes it may be necessary to wheel Grandma in with a wheelchair. And I was reluctant to do that on acrylic.

to wheel in grandma with a wheelchair

But that will not be so easy if you have to make a step to the shower because of the drains. It is more effective to plan for a good grab bar, a wide opening, and a shower seat stool.

By the way, the following applies

If stable, then solid (screed/concrete). But "wash me, but don’t get me wet" doesn’t work. You have to choose one of two options – solid and no longer accessible (whether sloped screed or tileable element) or classic with a shower tray

So it is due to the fact that sometimes it may be necessary to wheel grandma in with a wheelchair. And I was reluctant to do that on acrylic

Ok.
1. I hope you have planned enough space in front of the shower for that, because
2. you can only push a wheelchair over an edge forward easily with a nice flat ramp, or you do it - as usual - the other way round and pull grandma in.
3. Now comes the mental picture, because a normal wheelchair is about 70 cm wide. So you stand behind grandma, since you can only pull her in because of the step, and now have to shower her from behind. You’re either already halfway naked or feel dressed like you just jumped into the pool.

So forget the idea with the wheelchair and grandma. At least in a shower as narrow as yours.