After screed, mold or mildew stains?

According to the instructions, from the second day onwards, you should shock ventilate at least once.

And the windows were fogged up and dried?

In our case (anhydrite), they were dripping wet several times a day. :(

I also think that once is too little, especially in the summer, because warm air does not absorb moisture as well.

I would now consistently ventilate crosswise multiple times, wipe off the mold as quickly as possible, and set up a dryer.

I also think that 1x is too little, especially in summer, because warm air does not absorb moisture that well. ...

Warm air actually absorbs moisture well. However, one must not equate this with the relative humidity. For example: 10 °C air temperature, 60% rel. humidity: 5.6 g water/cubic meter of air 20 °C air temperature, 60% rel. humidity: 10.4 g water/cubic meter of air

Warm air in particular absorbs moisture well. However, this should not be equated with relative humidity.

For example,

10 °C air temperature, 60% relative humidity: 5.6 g water/cubic meter of air
20 °C air temperature, 60% relative humidity: 10.4 g water/cubic meter of air

Not at all, because warm moist air cannot absorb any more water at those temperatures.

Exactly not, because warm moist air cannot absorb more water at those temperatures.

But you only talked about warm and not warm moist (or even saturated) air, so is absolutely right. And in our latitudes, saturated air naturally occurs rarely. If the house is located in the tropics, of course, I said nothing. ;)

Actually, I am just a silent reader, but I have drying very well under control. My advice to : Do what already mentioned and get a dehumidifier that supports you when ventilating. At least three times a day, better four or five times. If for some reason you cannot get to the construction site that often, then rent several dehumidifiers and fans from the dehumidifier rental. The number of devices must be adapted to the size of the house. Mold and mildew stains should be removed as soon as possible with cleaning alcohol.

I myself have had excellent experiences with these things and can only recommend it. Yes, it costs money, but it is well invested. Better than ventilating by hand.