good evening guys I got a dehumidifier but I did n...

Black electrical tape, paint or even some thick paper or cardboard taped over the the are can block the light. --- That looks like a Peltier style dehumidifier. In my experience they do not do well. If sized properly they can get the humidity down to about 60% relative humidity but really lack the power of a compressor style machine to get to the desired 50% during flower. Still, something is better than nothing so give yours a try and see if it does what you want.