Alright, Im a pretty decent guitar player, rhythm and treble etc but the one thing I cant seem to get down is how to play rhythm while singing. Is the volume turned down? Should the chord progression be simple?

Not sure where to begin with this.

Thanks guys.
either palm mute, og simply play something, have a little break while the singer's singing, or turn up the volume for the microphone or turn down the volume on the guitar...

I Recommend having the microphone a bit louder than the guitar

about the chords i Recommend trying to have the same note as the singers singing, that sound best
Example: you play a C Chord, and the singer sings in that note, then you play a D, and the singer sings in that note, simple
but make sure to have exact timing, or else it'll sound stupid