I need your help to how to behave and not repeat my mistakes

Sorry for this long post and I really hope you can help me:

I have a question, is that I don’t know how to deal with this kind of persons and situation. I’ll explain to you:

I am very sociable, i want to be friend with everyone and I’m kind to everyone. Instead my group of friends are not like that, they don’t really socialize with others. So there is a guy that is very shy and he didn’t have too many friends. And I started talking to him. So we started spending time together, he met my friends.

So something you need to know from my group of friends is that they are very mean to each other of the group but just for kidding. I don’t really accept this behaviour. So the “shy guy” that started spending time with my friends well he became a mean guy (also just for laughing) but he doesn’t know how to moderate so he started attacking me everytime we meet because I was the nice guy with him. At first it’s cool but it’s a pain in the a\*\* now. I can’t talk to him privately because he will go report it to my other group of friends and they will attack me more.

I was just trying to be a nice guy and socialize with people because at first he was very kind. I don’t want to repeat the same mistakes and how can i deal with this, because I can’t stand being with my group because of his toxic behaviour and i need to see him everyday and eat with them all days.