How to close?

how can I close the DP2 application? It seems to stay in the topbar if I try to close it by pressing the “back” button and don’t see any other option…

Anyone? I just don’t know how to close the app on my Phone. Might seem stupid maybe, but some help would be appreciated…

using a Samsung s4 press the arrow button then hold down your home button and you should see "close all " works for me.
using Nexus 7 press arrow button on right (should see app min. ) drag to bottom
Best I can do