If the "picture-in-picture" function is activated on the Oppo smartphone, you can, for example, continue to watch YouTube videos in a small window, even if another app is currently being used. The window can be moved freely on the screen.

Android 10 | ColorOS 7.0
Step 1:  Open the  Settings
Step 2:  Tap on  App management
Step 3:  Tap on  App list
Step 4:  Tap on  App  you want
Step 5:  Tap on  Picture-in-picture
Step 6:  Enable or Disable  Picture-in-Picture
  1. Open the Settings
  2. Tap on App management
  3. Tap on App list
  4. Tap on App you want
  5. Tap on Picture-in-picture
  6. Enable or Disable Picture-in-Picture

Oppo Instructions