how do i keep the back button on at all times?

[Android Central Question]

When working on my phone I need to have the back button on, it disappears and I have to touch the bottom to make it reappear which doesn't last long.

 

[Rukbat]

An app that runs in full-screen mode will be covering it. If the app is full-screen and doesn't have its own back button, and needs a back button all the time, email the developer.