I'm running a microphone through a PA, and every time that i move the volume past 5 I get a screeching sound. Any tips?
Use a good microphone and close mike it. What mic do you have?
Gilchrist custom
Yamaha SBG500
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100

Cathbard Amplification
My band
You need to use an EQ (7 band or more) to isolate the frequency that's feeding back.

Hopefully your mixer has an onboard EQ and you can use that.

Usually, reducing 4K will clear that feedback right up.

Most mixers do have an onboard EQ.