Active Level 4
Many people must be knowing this but i am posting for those who don't know. 
When you are home and if you have wifi and don't use mobile data it's good practice to either use 2G or airplane mode (because if you are using 4g and your signal is weak then the battery drains faster). As our most important contacts are on whatsapp so they can call or message us on whatsapp. This way your battery will give more back up time. This helped me in m51.
Active Level 9
Expert Level 5
if you not done yet then do some settings to save more battery life and observe for next 1-2 days, it will give a noticeable difference

1. Connection>more connections settings> disable nearby device settings.

2. Location>improve accuracy >disable
A. Wifi scanning
B. Bluetooth scanning .

3. Device care>battery >power mode>select "optimised" and "adaptive power saving".

And then click on "app power management >
And enable these 2 options.
A. Adaptive battery
B. Put Unused Apps to Sleep.

4. Long press on each app specially 3rd party app(LIKE FACEBOOK, YOUTUBE) and rarely used apps and also ON "GOOGLE APP" as well, then click on>app info> go to these 3 options below on by one

A. Mobile data> allow background data usage>off

B. Battery >allow background activity >off

C. Notification >disable unnecessary notifications like promotional and unnecessary reminder notifications.

5. Go to settings> privacy > permission manager > location> and check which app have accessing your location all the time and if you not using that apps much, then deny access or set as " allowed only while in use"
As unnecessary location access by 3rd party app causing battery drain.

6.  Go to settings > Google > on device sharing> check which 3rd party apps present there for e.g. if you use paytm , paytm will  shared data to show recommendation and suggestion which also cause battery drain

7.  Go to settings > account and backup> account > check which app syncing automatically there, and if any app which not necessary to auto sync then click on it and "disable sync"

8. Go to settings >apps>search "weather" >click on settings icon right side > change "auto refresh" settings as per your requirements and disable some unnecessary reminder. ( due to auto refresh it continuously consuming battery)

9. If you use Facebook frequently then disable "auto play video"
And if you are mostly uses mobile, on wifi connection then also disable "auto play videos" in YouTube.

10. Google >click on 3dot at right top corner>usage and diagnostics >off this option.
Beginner Level 2
I am raushan Kumar
my phone is bluetooth and wi-fi not working
please reply
make new post..people will help you there...try resetting your mobile and check