The revision by Recluse is more concise, but still has the same problems the original post had - predominantly in the basic logic of the premise.

A Marine survives a ship crash on a remote planet, but to get out alive, he has to stop two fighting rival gangs of a mining town

The concerns that jumped to mind, when I read the concept, were about the causal connection of the events. As Dkpough1?pointed out, what is the reason he needs to stop the fighting? How does him crashing on the planet make him NEED to stop the fighting?

If it's just a writing connivence thing (we all do it once in a while?) there needs to be more causality, i.e the fight on the planet caused a missile to go into space and hit his ship which forced him to crash land. Other wise it's a random event that makes him take action. Better yet if he was sent to investigate or stop the fighting in the first place, and then he gets shot down.