Bootstrap navbar problem - not collapsing

Hi, at my custom template which I'm developing for a client: http://demo.kybernaut.cz/dirtweb/ the Bootstrap navbar is making troubles - when it should be collapsed (as mobile device size, xs) it's not collapsing and not even showing at all. Any ideas how to fix it? The same navigation is displayed as well in the bottom of the page. Does anybody have an idea how to fix it, please?