Does replacing the window bring any benefit?

Hello Karl-Steffen, There are landlords who don't care about that and only want the rent. If they then find mold, it is usually the tenant's fault due to improper ventilation. The world is not that simple. Best regards

I see it the same way and some landlords simply refuse. An expert should come who proves that the mold originates from the window.

Well, an expert costs money and the tenant will not pay for that. Replacing the windows is good and all, but other problems can arise. The current generation of windows is so airtight that no moisture can escape. This can cause condensation, which in turn can lead to mold growth. The very best are windows with integrated ventilation. But that will probably remain a dream for the tenant.