Switch off your phone.

Use an iOpener to loosen the adhesive beneath the rear glass. Apply the iOpener for at least two minutes. You might want to repeat this step several times during the back cover removal.

The adhesive of the Huawei P20 Pro is of moderate strength, however a hair dryer, heat gun, or hot plate may also be used if you aren't able to open the device with the iOpener. Be careful not to overheat the phone—the OLED display and internal battery are both susceptible to heat damage.