If an app in the background cannot be closed, we can force an app to close, but we would like to point out that this process can lead to possible application malfunction.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Apps
Step 3:  Tap on  Manage apps
Step 4:  Choose an  app
Step 5:  Tap on  Force stop
Step 6:  Confirm with  OK
  1. Open the Settings
  2. Tap on Apps
  3. Tap on Manage apps
  4. Choose an app
  5. Tap on Force stop
  6. Confirm with OK

Xiaomi Instructions