To verify your current version before searching for specific firmware files, dial in the dialer. This displays the Android version ColorOS version Important Notes for Manual Flashing

on a PC. Connect your phone via USB and follow the on-screen prompts to flash the official stock ROM. Check Software Info

If you are looking to manually flash your device to fix a software issue (like a boot loop): Chipset Matters OPPO A5 2020 Qualcomm Snapdragon 665

If your phone is running slow, try clearing the app cache or updating apps through the Google Play Store before resorting to a full firmware re-install. of ColorOS, or are you trying to fix a specific software problem like a boot loop? Update software – OPPO A5 (2020) - Android 10 Guide