what are some bad language in chinese that I should know?

lots of them. mostly you can see such words as cnm, fw for example. first one is 操你妈（草你妈，肏你妈，choose which one you do prefer better) something about sexual intercource with opponents mother, the other one is 废物，which is basically translated as a trash.(垃圾can be used toward the person too） 傻逼 is also a usual swearing, that basically can mean something from dumb fuck to the moron or smth. 抠逼 maybe can be translated as square, not sure.