If you cannot receive the OTA notification, you can update manually using a firmware file. Oppo A5 (2020) - Full phone specifications - GSMArena.com
: The OPPO A5 2020 (CPH1933) originally launched with ColorOS 6 (Android 9) and has since received updates to ColorOS 7 (Android 10) and ColorOS 11 (Android 11). OPPO Software Update : Step-by Step Guide oppo cph1933 ota update