Adding hamburger menu ONLY for mobile view and NOT desktop view

Hello,

My client has custom navigation for her site in desktop view. Instead of accessing pages through the hamburger menu or tabs, we are using buttons (as seen in attachments).  Because of this we don't have any pages in the "Main Navigation" editing section and all our pages are in "Not Linked". This then means that in mobile view we do not have anything in the hamburger menu and you still need to click on our custom buttons to navigate the site. The problem is that when viewing the site in mobile view, the website looks cluttered. I was hoping of hiding the navigation buttons and instead using the hamburger menu for mobile's navigation.

Is there a way to have pages in the hamburger menu but ONLY for mobile and NOT desktop view? 

The attachments show what desktop and mobile view look like for our site. It also shows what happens when you click on the hamburger in mobile.

Hi,

What is site url? We can check problem easier