"there are 2 sides to every story" what does this mean?

It means, there's not just 1 argument. Someone might think you're lying, or someone might think you're telling the truth, stuff like that. There are two sides to every argument means just that. It doesn't refer to one side or the other, simply to the fact that there are two. The other side of the coin refers to the opposite argument. So saying "on the other side of the coin" is similar to "on the other hand"

do you want me to proof read it?