My.apologies for not being so clued up...performed ota update and battery is now worse...do I now need to do factory reset?..how do I do that without losing all my information on phone?? Tutorial??

Bought bv8000pro at Christmas..suddenly battery life.is terrible..losing roughly 20% battery life within 2hrs of being idle...please help..at this rate it won't even last an 8hr work day.
.