Sidebar below main page content in mobile view

Hi,

I have purchased the Pro GeneratePress and am trying to set up a menu on a content page - see here: https://zionfellowship.us/gp/academics/

My problem is that when viewing the page in tablet or phone width, the sidebar goes under the main content which is not ideal. Is there a way to make the sidebar to stay at the top of the page?

Also, a side question: do you know a good plugin for widget/sidebar menus that can appear like the following?: https://www.lutherrice.edu/degree-programs/

I purchased a plugin called Advanced Sidebar Menu Pro, which is alright but does not work well with the mobile view. I like the lutherrice.edu menu in that it reverts to a single accordion style button for a mobile view.

Thanks for your help,
Daniel