Insects will fly in via the gap between gaps too, right?

hi all,

i have a exhaust fan mounted on my toilet window just like the above. However, my toilet still feels very "wet" and already have mold on my plaster ceiling although I just move in 8 months ago.

Contractor previously told me my condo is quite old (14 years) and has house sweat. Whatever bullcrap that is. I even have molds on my PVC in the masterbedroom and shirts which I havent worn for a long time. How do I get rid of molds?