Connect your iPhone to the computer then launch iTunes or Finder.
    While your device is connected, quickly press and release the Volume Up button.
    Then, quickly press and release the Volume Down button.
    Finally, press and hold the Side button until your iPhone screen turns black.
    Keep holding the Side button when the screen turns black and then press the Volume Down button.
    Hold both buttons for 5 seconds.
    After 5 seconds, release the Power button but keep holding the Volume Down button for another 10 seconds.
    If the screen remains black (no logos or text) after 10 seconds, it means that you have successfully entered DFU mode. After a few seconds, you should see a message saying that “iTunes has detected an iPhone in recovery mode and that you must restore it before it can be used with iTunes.” If you see this pop-up message, select the option to Restore iPhone. Doing so will trigger iTunes to instigate the system restore. Just follow the onscreen commands to finish restoring your device.

After successfully restoring your iPhone, you can exit DFU mode by performing a force restart on your iPhone 11.