I Need Some advice for P7-L10

Hi All hope you doing good.. My phone was working fine but suddenly my battery started to drain like I left it on 40% at night and in morning the phone was out of power and time was 5:00am 1/1/1970 (not used during that time) now it takes even long to fully charge the battery which lasts only 3 or 4 hours max. Everytime it get out of battery it changes date and time so I set it manually or connect to internet so it gets fixed.

Advice me should I replace the battery or it is some issue with some chip of board or someother issue?

Please do suggest me solution if possible thank you all...