-Try adding apps to sleep. -Use dark wallpaper and themes , and Do not install any 3rd party apks from websites. -Use the device in medium power saving mode. -Uninstall lesser required apps from your phone and keep an eye on which app is using more power and clean its cache and uninstall if you don't want it to be use that much of battery. also turn off background location services. and Bluetooth, Wifi etc if you are not using. if nothing works Try a factory reset once, take your Data backup before resetting.
