Even if i close all apps this app remains as it is. It is not closing showing small lock on right.

[VINAY5EFE]

Even if i close all apps this app remains as it is. It is not closing, showing small lock on right top corner, How to close it or how to remove lock, please do the needful. Screenshot of mobile is attached.

Android mobile Manufacturer: One Plus,

Model Name: One Plus 6 and the

Android OS: Oxygen OS version 10.3.5, updated recently.

[Bernd Alheit]

Swipe up from the bottom, hold, then let go. Then swipe up on the app.