Bro, you want to hide navigation bar or you want to hide apps? First check what themes are you using, default or downloaded one? change your theme to default one
Now,if you want to hide navigation bar, then change navigation bar setting i. e use full screen gestures in place of navigation buttons, after this you can find option to hide gesture hints and able to use full screen without navigation buttons or navigation gestures
To hide apps, go to settings>select display>now click on home screen>here you will find tab to hide apps>click on hide apps tab(sometimes downloaded themes affect such settings)
NOTE: YOUR QUESTION IS NOT VERY CLEAR, SO I TRIED TO COVER EVERY ASPECTS RELATED TO YOUR POST..IF STILL YOUR QUERY REMAINS UNANSWERED, POST IT AGAIN WITH THE SCREENSHOT..
Bro, I think..now it's not available..you can use gesture navigation(shared above) or in game launcher you can hide your navigation bar or lock it..please correct if I am wrong..because what's available,I already shared the screenshot..