JG BAR-10 problem

Hey, im sorry for the recap of this question over and over again, but when I did some research I didn't really understand what the people were trying to say. So basically the problem is everytime I shoot it would either curve more to the left or more to the right, I know the problem is the hop up, but the thing I don't get is how am I going to fix this problem. I have tried dissassembling it and reassembling it, but it wouldn't work. And everytime I try to zero the scope in it obviously wouldn't work so I have tried that for like hours. So I heard you should sand it, but it isn't good for the hop up system. All I know is I greatly appreciate it if someone give me a in depth explanation or make a video and sorry again for bringing this topic up, I really have been searching up info, but I didn't quite get it as much