When you play your recording back (or when you actually doing it) check the levels at the bottom of the screen, if they go to high there's 2 little red boxes at the right hand side that light up.

If its just a fuzzing sound then when youve done your mix go into effects & then noise reduction, an then I think there's one called hiss & fizz eliminator or something. Go into that an you can actually get rid of any background hissing but if you have to get rid of loads it may make your mix sound a little duller.