Navigation menu works the wrong way

Navigation menu(black areas in our website. it has Home, About Quarks, Community, Getting Started, etc) seems that works the wrong way in mobile site.
It works properly when larger screen device but in case of mobile device(I've tested my android phone) works unintentional collapse when I clicked submenu.
About Quarks or Community(its 1depth menu) has their own 2depth menu like below:

So, When I click on, the 2 depth menu should be shown instead of the collapsing whole menu