How can I become friends with them and why they act like that?

So there's a guy in my class. He's really smart and he reminds me of my friend (from another school), which I have a great friendship with. He likes history and all, which is cool because it'd be fun talking or just listening about this.

I tried to speak with him a few times, smiled at him but DAMN. Idk why he's like that but when I try to make a joke, say or ask about something to make a conversation, he just smiles and turns away or getting defensive (it happened once) but there's NO WAY he'll anwser me.

Does anyone of you knows why he acts like that?