If you are resetting the phone to sell it, ensure you remove your Google Account in Settings before the reset to prevent Factory Reset Protection (FRP), which requires the previous owner's credentials. Troubleshooting
A hard reset deletes all internal storage data, including photos, contacts, messages, and downloaded applications. Back up your files to Google Drive, the OPPO Cloud, or an external computer. How to Hard Reset OPPO F5
Here's how to hard reset OPPO F5 using OPPO Recovery Mode: If you are resetting the phone to sell
Before you proceed, please note that a hard reset will erase all data on your device, including contacts, photos, and apps. Make sure to back up your data before performing a hard reset. the OPPO Cloud