Hi gavner,
That’s a great feature of this template, I don’t know why you want to disable it :((
If you want to achieve that you can remove css file for mobile device
<!-- MEDIA QUERIES -->
<link rel="stylesheet" type="text/css" href="<?php echo $this->baseurl ?>/templates/<?php echo $this->template; ?>/css/layout-mobile.css" media="only screen and (max-width:719px)" />
<link rel="stylesheet" type="text/css" href="<?php echo $this->baseurl ?>/templates/<?php echo $this->template; ?>/css/layout-mobile-portrait.css" media="only screen and (max-width:479px)" />
from file: templatesja_lensindex.php
However, this only helps you to have menu like desktop version, this template has the combination of jQuery Masonry plug-in and jQuery Lazyload plugin so it still keeps the reponsive design. You cannot disable it.