My friends are in a huge fight and I can't fix it!?

you should just have a rematch!

Don't even attempt to fix it. Let them work it out by themselves no matter what the outcome may be. You can't change others, you can only change by and for yourself.

You can't fix it because it's not your argument, it's between two other people. What makes you think you can fix someone else?

The only person you can fix in this life is you.

Correct. And it's not your responsibility to fix it. Butt out.