Yes, you can try updating to flyme 6. Just remember to cleardata to get the best performance out of it. You can find firmwares here https://downloads.meizufans.eu/
Draining is usually caused by apps running in background
Please check what is using your battery through Settings -> Battery -> Ranking.
If none of these work it is likely a battery problem and you either need to recalibrate the battery (charge to 100% and drain multiple of times) or get a battery replacement.
thanks for reply bro i did all of thise recalibrate and flash flyme 5 when the problem still and i find the problem on Settings -> Battery -> Ranking. cell standby drained all battery… i cant fix it and i buy thise phone for 1 week only how thise happend ?? (when u say updating to flyme 6 how ?? because i have global meizu m5 model m611h with flyme 22.214.171.124G if i can update tell me how pls and thanks (soory for my bad english)