Oppo
Turn On/Off Background Data for Apps auf Oppo
Background data controls whether an app can connect to the internet while it is not open on screen. On Oppo phones running Coloros, this setting is enabled by default for most apps, which is why chat apps, mail clients and social media normally push notifications instantly.
When background data gets switched off for an app, the system blocks its internet access as soon as you leave it. No new messages arrive, sync stops, and widgets tied to that app stop updating until you open it again manually.
To check or change this per app, go to Settings ➔ App management ➔ App list, choose the app in question, open Data usage details, then enable or disable Background data.
Turning it off can help reduce mobile data consumption and slightly extend battery life, especially for apps you rarely need live updates from. It is a reasonable fix if one app drains your data plan or keeps waking your phone, but disabling it for messaging or email apps means you will only see new content after opening them.
If notifications are missing for several apps at once, check whether a battery saver or data saver mode is active system-wide, since that can override individual app settings.

