Mold/humidity in house

I am contacting you because I would like your help about how to proceed with my landlord/ house agency. Since more than two years ago we have requested to have the house checked because it's very humid and moldy at times. There was not a positive reply from the agency, at some point they even stopped replying and we ended up cleaning the mold on our own (without though solving the underlying cause of it). Due to personal reasons I had to stop pushing the agency but a few months ago we resumed the topic. The agency keeps on ignoring our request and after a lot of pressure they sent a painter in the house who had a look and was supposed to arrange an appointment to fix the wall but never contacted us again. I phoned the agency because we were expecting someone to come and check what the underlying issue is and not just a painter. One office worker from the agency (who has not visited the house) said that the issue is the ventilation and the high temperature in the house, but as we explained to them, we ventilate the house daily and never put the heating higher than 19 degrees. The agency told us that they will not take care of this and that we can solve it on our own and if we figure that the issue is their fault then they will pay for it. In the mean time, since it's raining more this month, our walls are becoming more and more moldy. Also, the humidity is very high, causing us to be sick very often when spending many hours in the house.
I would like to ask your advice about how to proceed, the situation in the house is very unhealthy and we don't know what to do anymore. If needed, I can share the communication we had the past two years.

PS, we contacted the huur commissie but as we’re in the private sector and paying almost 2,000€ the said they cannot help us unless we have permission from the landlord to contact them, which we don’t have.