Damp walls in the basement of a new building - construction execution error?

No, that would not mean that the water is coming through the base plate. It simply means that you have water in the screed insulation layer. This water can also penetrate because, for example, a lot of water was splashed around, and thus the water gets into the screed insulation layer via the [Estrichtandstreifen].

Short update:
There is a (construction) fan with 70 watts placed directly in front of the corresponding spot, and it has improved.

But somehow it’s clear that it gets better in the short term when a blower is placed directly on it. We will continue to wait and hope for the best..

The longer the moisture remains in the screed insulation layer, the higher the likelihood of mold growth.

Do not work superficially with a dryer!

The underfloor heating is also running, and I will not save on heating in the basement in the future either. Or what would you recommend? A standard [Bautrockner]?