How many coats for good coverage?

But that is dispersion. I would only use silicate paint

And I don't think the GU/painter intends to use that anyway...

I painted our raw basement with Sto white, this paint is absolutely amazing, one coat was enough and the concrete was completely covered, but until now I only knew hardware store paint.

I painted our unfinished basement with Sto white, this paint is absolutely amazing, one coat was enough to completely cover the concrete, but until now I only knew about hardware store paint.

What is the exact name?

Either Sto in or Rapid.

The painter is painting with "Relius Silat Bio Interior Silicate Paint". The walls look good so far, but the ceilings, especially in the attic where drywall is installed, still show light-dark shading in some places. According to the general contractor, one coat is in the contract. However, in my opinion, it must be opaque. We included the painting service in the contract so that we don't have to paint again..... Otherwise, it doesn't make sense to me.

The walls look good so far, but the ceilings, especially in the attic where drywall is installed, still show some "light-dark" shading in places

Ceiling paint:
1–2x RELIUS SILAT BIO INNEN, undiluted or max. 3% diluted
The ability to touch up depends on several parameters. Please also observe the BfS information sheet No. 25. We recommend extensive touch-ups

As the manufacturer usually says. 1-2x

How was the priming done?