After the update, the phone became hot and the battery backup decreased. Please show me the solution

Force-restart your phone:

• Press and quickly release VOLUME UP

     then

• Press and quickly release VOLUME DOWN

     then

• Hold the SIDE button until an Apple logo appears (15-30 seconds), ignoring "slide to power off" if it appears

The operative word here is QUICKLY; and try it a couple of times, the timing is a little tricky. If done correctly this will always work unless the phone has a hardware problem. 

And wait a day or two after an update for the new version to do “housekeeping” - reorganization of system data - which can require extra energy.