1.OPPO official website-coloros-ROM download, find the corresponding model, and click enter to see a "version history". Click on it, then download the previous version as required, save it in the root directory of the phone memory, and back up the important things inside the phone.

2. Turn off the phone, hold down the volume at the same time, then hold down the power button to enter recovery mode, clean up all data, click "Install upgrade file" to find the stored firmware package, and click Upgrade.