I'm no authority as my French is pretty rusty but it's formally "bon jour" (good day), informally "salut" (hello) and also informally "ça va" (how's it going) which can be replied with the same "ça va" (it's going). I would recommend you post in French Questions, though. This is English.

Oh yeah sorry i forgot i learned some French at college last year but i forgot how do i say hi

In French we say "salut" to say "hi". You can also use this word to say goodbye.