How to Flash Xiaomi Firmware using Recovery
In a case where you can still access your data partition, or just want to update your firmware using the recovery, the following steps will deem useful.
Download the ROM file compatible with your device, and rename it to update.zip.
Transfer it to the root of your internal storage.
Proceed by booting your Xiaomi device into the recovery mode by pressing both the Power and Volume Up buttons together.
Once you enter the recovery mode, you can navigate using the volume up and down keys, and use the power button to select an option.
Scroll down and select the “Install update.zip” option, and give your phone a while to do the task.
Once done, if you phone doesn’t reboot automatically, just navigate and select the “Reboot” option from the recovery.
https://www.getdroidtips.com/guide-flash-miui-rom-xiaomi-devices/#How-to-Flash-Xiaomi-Firmware-using-Recovery
Télécharge la recovery rom version Europe la plus récente ici et appliques le tuto au dessus : https://www.getdroidtips.com/poco-x3-nfc-flash-file/#Pre-Requisites
Ça devrait marcher mais toutes les données dans ton espace de stockage interne seront supprimés