The Xiaomi Mi A2 Lite main firmware on this page will help you upgrade/update the phone version, relocation from Beta to Steady ROM (vice versa), un-brick or restore your device to its default factory state. Constantly backup existing firmware prior to flashing any firmware.
How to flash Xiaomi firmware
After downloading the firmware from above link, get a practical USB cable, then follow the guidelines by means of this link to learn how to flash Xiaomi fastboot and healing firmware