Responsive issues - portfolio parallax

Hi
I have a couple of unresolved issues which I need to sort out before I can properly launch my site concerning the home page mobile
the portfolio parallax – there is a large gap between the bottom row of images and the bottom. This is a problem on tablet (narrow/portrait screen) and on smartphone when using desktop view. In normal view on smartphone, I have a different problem – the 2 row of images seem to have changed into one column with the only the top two images visible.

  • another issue which relates to site responsiveness on mobile devices, so I’ll include it here. On both smartphone and tablet the dropdown navbar links are not responding on all parent pages. In the case of this site, this affects the Welcome, Destinations and Terms & Booking page. The problem resolves itself when I change to desktop view. These are the final two issues which I hope to resolve so I’d very much appreciate your help. - the site is http://www.guided-mountain-walks.com
    Thanks

I have played around with a bit of CSS and more or less resolved the problem of the space below the images but still only one column showing of mobile - would really appreciate some help with this.