The banner notifications on the Huawei smartphone are small pop-up windows that pop up for a few seconds on the status bar to inform us about a new notification.
This notification method is mostly used by social media and messenger apps, such as Facebook, WhatsApp, Telegram or Instagram. The banners can be allowed or blocked individually for each app.

Android 10 | EMUI 10.0
Banner notifications -  Open the  Settings
Banner notifications -  Tap on  Notifications
Banner notifications -  Choose an  app
Banner notifications -  Tap on  Miscellaneous
Banner notifications -  Enable or disable  Banners
  1. Open the Settings
  2. Tap on Notifications
  3. Choose an app
  4. Tap on Miscellaneous
  5. Enable or disable Banners

Huawei Instructions