There is a wi-fi router emitting radio waves (wi-fi) in a room. The room has solid walls but also a thin anti-mosquito net door and that net is made of metal (I think, but I'm not sure).
When I am outside of the room, the wi-fi isn't working so well but when I am outside and open the door it is working better, so can that mosquito net (if made of metal strings) act as a Faraday cage and perhaps absorb or block the wi-fi signal?
The question is not well posed. The metallic mosquito net of the door is a flat rectangular sheet, not a closed surface required for a Faraday's cage. The mosquito net prevents the transmission of electromagnetic waves in the cm range through the door similar to a contiguous metal sheet. The microwaves of the Wifi transmitter in your room (and vice versa of your wireless device) can, however, go through the walls around the mosquito net door. When you open the door, in particular, when you stand close to it the microwaves can also go through the open door thus increasing the intensity of the waves so that the Wifi seems to work better. If the mosquito net covered the door, all the walls, ceiling and floor of your room this would constitute a Faraday's cage. Then no electromagnetic waves could escape (or penetrate).
