ᐅ The wall has uneven discoloration. What can be done? New construction.

I think the main issue here is that the direction of painting wasn't followed. And cheap DIY store paint?

Place furniture in front of it??

The window is really striking, and that small triangle... who designs something like that? What type of paint was used? Was the surface preparation uneven? Was it a DIY job or done by a painter?

Attached are more pictures.
Pufas Grundierweis GP 5 was used as the primer. The final coat is Herbol RF paint. Both are actually painter’s paints from a specialist supplier.

It is unfortunately difficult to see this clearly in the pictures.
The staircase appears narrower in the photos than it actually is. The corner at the top left is due to our Frisian gable. The wall has already been well primed and painted twice. Before priming, the wall was already uniformly white.

We sanded the plaster beforehand with a sanding tool. The plaster reacted differently to sanding. In some areas it was smoothed off completely, while in others noticeable sanding marks remain. Therefore, we chose Herbol RF because it offers good properties while still having a high filler content.
Perhaps the appearance is also influenced by the fact that the substrate varies in texture (partly rough, partly smooth).

P.S. Painting is always done in the same direction per wall.

In my opinion, this is an issue related to the lighting. I hardly believe it can be improved with paint. Probably best to just accept it as it is?

We suspect that as well. However, I thought it could still be improved.
Yesterday, we painted two more rooms. The same issue appeared there too. The light incidence is similar in those rooms. You can only see it when looking at the wall from the side and against the light.
It is quite frustrating for us.