Sorry to hear about your battery problem.
There are several things you can do to increase the duration of your battery charge.
First make sure that your charger and/or your battery is not at fault.
If you are certain that they are O.K., then you can take the following measures until a real solution is found. Then you can take back what you have done by undoing the changes:
1) Turn off background app refresh
Settings>General>Background App Refresh ( Turn off those apps that you do not constantly need to be refreshed )
2) Turn off Auto-brightness
3) Reduce Screen brightness
Settings>Screen and Brightness> Bring the slider to halfway
4) Reduce visual effects
Settings>General>Accessibility>Reduce Motion ( Enable/Turn on the setting )
5) Turn off "Hey Siri"
6) You must also remove or update the apps that are not compatible with iOS 11 in their present state. They may deplete the battery quickly enough if not removed or updated to be compatible with iOS 11.
Hope this helps.