Apply a heated iOpener or a heat gun to the screen to loosen the adhesive underneath. Apply the iOpener for at least two minutes.

The protective adhesive of the Redmi Note 9 is very strong and it's hard to get underneath the display panel in the beginning. It is likely that you have to reapply the iOpener more than once.

A hair dryer, heat gun, or hot plate may also be used, but be careful not to overheat the device.