I'm in a new school in my country because when you're 15 you choose a school that you want and study it for 4 years.Because of this I also have new schoolmates and some of them I like and some I don't.There's a guy who just keeps on wanting to fight me for no apperant reason.I joke with him but he just says"what are you laughing at or you think this is funny?".And they he tries to grab me by the neck or punch me or kick me.So we get in an argument then he starts acting like a little bitch for 10 minutes and we're back at it again.The problem is he's 20 cm taller than me(I am 180cm) and lifts but I also lift but not as long as him.He basically tries to fight everyone at any given chance.

Also I don't know how to react to insults,confronations,example: Today me,my 1 good friend(we're somewhat popular),other guy who has significally higher SMV(somewhat friends) and the guy who tries to fight just came when we were hanging out because the high SMV guy knew him.Then the high SMV guy and the one who wants to fight were in a store.Then they said something about my dick and I responded jokingly.But then we came to school and we were outside when they said for no apperant reason that I need to sit dow n and he pushed me to a bench(the guy who wants to fight),so why was that?I try to keep my distance since he's retarded but he keeps on trying to make contact with me.

So my question is why is the guy always trying to fight me and how to respond to people insulting/roasting me?