Since you are their child, it is not your issue, not your fight, and not your final decision.
I understand that you want your parents to stop fighting- any child does, given that almost any parents fight. But you must recognize your place in the family. I am not saying you are too young to be able to deal with these kind of things, but just because you are ABLE to does not mean you should.
Your parents are adults, and this is their fight. You coming in the middle of it and saying you want them to stop....won't make them stop. Fighting isn't something that is just cut off. Usually the opposing sides wear out or the issue is resolved- so you simply need to be patient