After upgrading, my battery runs out completely overnight

It could be the indexing service, it should self correct in a few days.

After upgrades its best to keep it plugged in overnight for indexing.

You can also check the battery under setting and look at its health, or if any other background app consuming the battery.

If you updated to iOS 13.3.1, using Wi-Fi, try again to use iTunes on your computer and restore from the backup you made before.

If you create an encrypted backup, it will also contain your passwords.

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Why don’t you just leave it plugged in overnight? It’s a best practice, and if you enable automatic backups your phone will be backed up to iCloud every night.