Sorry to hear that Alena,
When your iPhone’s battery is getting low, switching to Low Power Mode is a simple way to get more life out of it. You can enable this feature by going to Settings > Battery. By turning on Lower Power Mode, you can lower the brightness of your screen, speed up your iPhone, and limit the number of animated UI elements that use a lot of power. It’ll also restrict the “Mail” app to stop downloading data and other services like iCloud sync, and AirDrop will not run in the background. However, you will need to enable the Low Power Mode every time you charge your phone.

If you start noticing an abnormal drain after installing an iOS 14.4 update, we recommend you restart your iPhone before doing anything. Power it down, wait for a couple of seconds, and restart. A quick restart will have a tremendous impact. However, you can also reduce the screen brightness and use a lower power mode to see if it helps.

And yes, you can downgrade back to the previous version of iOS, but in that case, you can’t restore from an updated version backup. That means if you’ve backed up your iPhone since you upgraded to iOS 14.4, you can no longer use that backup if you choose to downgrade.