I am using SP Page builder, latest release with the Helix Ultimate template. I also have had to use DJ Megamenu because the helis does not support subtitle text under menus, however I do not think this is my issue
If I go to any page, and test the responsive nature of it, the title and text n the sp page move over the top of the menu bar, and on phones shrink to an extremely narrow width, around 1 quarter of the availabel space in fact, so on phones it looks silly