A force restart is sometimes casually called a hard reset, but it does not erase an iPhone 11. Use it when the phone is frozen or will not respond. A factory reset is a completely different procedure that deletes your data.
- Quickly press and release the Volume Up button.
- Quickly press and release the Volume Down button.
- Press and hold the Side button.
- Keep holding the Side button when the screen goes dark, and release it when the Apple logo appears.
If you actually want to erase the iPhone 11, use Settings > General > Transfer or Reset iPhone > Erase All Content and Settings after making a backup. Do not use that erase option merely to fix a frozen screen.