Seems a little issue with the sticky header in the mobile version, it’s working well when opening the mobile view on the desktop but when opening on a proper mobile device so it’s not working properly (don’t stick during scroll and even cropping from the left side). (Refer to snapshots).
the issue isn’t with the Mobile Header – its because part of your page content is wider then the viewport which causes horizontal overflow allowing the page to be scrolled sideways. It looks to be the Section “Why Choose Us” you should fix whatever issue there is with that section to stop it from overflowing.
Failing that you can add this CSS to stop anything overflowing: