Screed no functional heating after 7 weeks

Please, please do not ventilate at all for the first 3-4 days! After the screed is installed, it always becomes unbearable inside the house. The reason is the chemical reaction during setting. The water that condenses is not only the water from mixing, but also a reaction product during setting. And this lasts for 28 days with cement screed. When the screed has been inside for a week, ventilate twice daily by fully opening the windows. No tilt position of the windows!!!!! Additionally, wipe the windows and frames with a sponge cloth or similar to remove the moisture. Why it is so pronounced in one room, I cannot say as I do not know the building. I am not familiar with a ventilation protocol. There is the heating protocol. The photos shown are completely normal. Wipe down, ventilate. Spray the plasterboard with anti-mold spray to prevent it from getting worse.

Then it's about time. The drywall boards also warp due to the extreme humidity.
Well, legally responsible is the developer. But that rarely works. So do it yourself, after all, it is your home. At least then you know that it’s done. Report the mold as a defect in writing. Spray it yourself before it’s too late. The developer won't tear anything out, then follows a legal dispute, expert opinions, and things you don't need. It is the faster way. Claim a reduction in value during the final inspection.
In which federal state are you building?