Menu text overlapping

Why is my menu overlapping my text below when you have a chrome or IE window not completely open. If you size down the browser window fully it gives the hamburger but if you don’t the text overlaps. I am using older template 2.1.2 but I am afraid to upgrade due to lots of customizations with seo etc. What can I do to make this responsive on browser windows. Works perfect on mobile devices. ThHanks in advance. Website is http://www.renowaterfilters.com