iPhone battery is draining fast

Changes in software such as upgrades may introduce new features which may add to power drain and heat generation. Check Settings > Battery feature to see if there are apps or services running that use a lot of power. If there are, decide if you need them running all the time, can turn off a service when an app is in the background, or disable the feature completely. Read this support article to learn about the battery health feature. —> iPhone Battery and Performance - Apple Support

Refer to this post for good tips on reducing battery use on your device --> https://discussions.apple.com/thread/255063652?answerId=259418848022#259418848022

Addendum to #11. Use 4G/LTE instead of 5G. Use 5G with your iPad - Apple Support

Here is a related post in the context of device heating. --> https://discussions.apple.com/thread/255063343?answerId=259418333022#259418333022

Where did you get this phone? Apple stopped selling the iPhone 11 about a year ago. If this phone has been sitting on a shelf somewhere for a year, that could have affected the battery.