Huawei
Enable or Disable Background Data and Roaming for Apps auf Huawei
Background data lets an app sync content while it is not open on screen. Turning it off for an app means it only fetches new information when you actively open it, which is why messengers or email clients suddenly feel delayed.
Roaming data is a separate switch. It decides whether an app can use the internet through your carrier abroad. Leaving it on for every app can lead to charges you did not expect while traveling.
Where to change it
On Huawei phones running EMUI, both switches sit in the same menu. Go to Open the settings ➔ Tap on Mobile network ➔ Tap on Data usage ➔ Tap on Network access ➔ Open the menu ➔ Tap on Advanced network settings. From this screen you activate or deactivate background data and roaming data for each app you want to restrict.
Test the change on a messenger app first. If you switch off background data for WhatsApp, messages will only appear once you open the app, not the moment they are sent.
Use this per-app control when you want to limit one specific app, not as a general data saver. For an overall reduction in data usage, a dedicated data saver mode is usually the better option.