Window brand - Which window supplier to choose?

He just said: "That doesn't look nice."

This is an exciting topic! On the internet, you can find a blog post by a specialist lawyer titled "Abstand der Rollladenführungsschienen zur Fensterbank". More questions from answers ... . I'm curious how it will continue and if I remember, I'll take a look at it at our place ...

Sidebar:
This is one of those cases where it would be helpful if the builder showed the customer beforehand what it would look like. Our marble window sills also looked completely different from those in the showroom. My tip, to place realistic samples (with all the beautiful inclusions and imperfections, all of which are permissible and do not constitute a defect) in the showroom, somehow wasn’t understood. At first, we were quite confused [Schmutz kam allerdings noch dazu].

Honestly, how do you want to get the rail of the roller shutter lower? Destroy the protective cap?

If I am not allowed to have a distance greater than 8 mm according to the rules, I have to attach the guide rail next to the protective cap. I don't have to think about that for long.

Yes, there is a DIN that specifies something about 8 mm. Basically, metal always needs some space for expansion. As I understood it: ... it is often installed so that the guide rail rests on the window sill rail (as can be seen in your case) and this is _not wrong_ because it ensures that the windowsill is easier to clean. Thermally, this gap is not relevant. Pedants focus on the 8 mm and then later get annoyed that dirt corners form on their windowsills because they cannot clean under gaps smaller or equal to 8 mm. That is the difference between theory and practice! This is my layman’s half-knowledge on this topic.
Regards

If I am not allowed to have a larger gap than 8 mm according to the rules, I have to attach the guide rail next to the protective cap. I don’t have to think about that for long.

The protective cap will be plastered in, how do you want to solve that then? Without there being a gap from the wall to the rail?