Normally, apps can be terminated on the Samsung device by closing them via the background apps. From here, however, the app is only instructed to complete data processing and terminate background execution. However, this does not always work, especially if software errors are present.

You could now exit the app by restarting the Samsung device or forcing the app to stop, the latter works via the app info in the settings.

Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Apps
Step 3:  Tap on desired  App
Step 4:  Tap on  Force stop
Step 5:  Confirm with  OK
  1. Open the Settings
  2. Tap on Apps
  3. Tap on desired App
  4. Tap on Force stop
  5. Confirm with OK

Samsung Instructions