Looking for accessible video editing app

Hello,

Whenever I do a standup comedy gig, I always video my set and upload them to YouTube, however the last couple I've done the video is really unclear. Something else was going on in the room next door to where the comedy night was and you can't really hear my voice.
Is their any type of software or app that will let me edit the sound to make the background noise quieter?
The videos were filmed on my iPhone, but I'm not bothered whether the software is for Mac or iOS.

Thanks