I mean honestly you can't do nothing about it, if they want to beat you cause of that you have to take it and move on. You listening to people to act tough in front of them. That won't get you nowhere, your gonna piss them off more than they want to beat the shit out of you even more. There's like 10, if you beat one up or all of them; they are going to come back again to get you with more people. They won't stop until they get you... even if you threaten them you are gonna tell the Cops about it. They don't give a fuck about it, it just shows that you are a pussy and will make fun of you of that. Once they found you to beat up, they will literally beat you up. It's life, your mistake now you gotta suffer the consequences to your mistake. For every mistake theres a consequence to it... Don't listen to people to get a gun, knife and etc. Your not gonna get it, it's a damn straight fact.
I'm telling you this from experience. I got into gang problems, fought with another team member in a fist fight. Than, insult it the shit out of him in front of everybody because he started to insult me, than left with my friends. The next day he threatens me he's gonna fight me and until he doesn't win he won't stop. On my birthday I went to get a haircut, met him face to face. I said ok, he's the same age as me. There were like 2 24 year old behind him to back his ass up. I started to beat him up, than when he was on the floor. The 2 24 year old picked me up, held me and started to punch me brutally. Than when he got backup he took me down on the floor and started to punch the shit out of my face. I was bleeding from my forehead and this old lady saw it. Stopped it, called the cops, they ran. I went home, and it was end of it. I could involve my friends into it, but I don't want to because in the end when they are alone they will get fucked up.
You stole a material, and I fucked up this kid also insulted him. For that I got fucked up and for you... I don't know.
If I were you this is the best shot... Tell your parents about it, than let those retards come to you. Make sure your parents are with you, appologize about it. Tell your story than shake hands. End Of it.