It is only a 1080p phone so I don't think that brining it down to like 720 would make it perform that much faster but there is no "Resolution" settings on Android Phones. There is DPI though and if your phone is rooted there are apps that allow you to bring down the DPI which is the same as lowering the resolution but again that is only if it can be rooted.
You might be better off going to XDA Developers where you can most likely find more.