Hi Bella_1954
Sadly some updates do cause iPhones to work harder [generating heat], they usually settle down after a few recharge/restart cycles.
If you contact Apple Support they can diagnose any battery issues or whatever.
Turning off Push and changing to Fetch Manually helps [see SravanKrA's tips above] as well as turning off Background App Refresh.
Check Settings>Battery to see what is using the most power and adjust that app if you can. If you know an app using the most power is one you close properly then definitely do a Force Restart - this clears up any legacy issues that have carried over from before the update [if you left a lot of apps 'open' when you update, this can happen] -
Force Restart: In quick succession: Briefly press & release the Up Volume, then briefly press & release the Down Volume, then press and HOLD DOWN the Power Button, and keep it held as the screen shows the power off slider, still keeping the Power Button held while the screen goes dark and keep it held until the Apple logo appears, then release it. The phone will restart, hopefully a lot cleaner than before.
best of luck.