Admin menu bar covers part of the screen while working in mobile mode
There is no configuration settings at admin/config/administration/admin_menu for hiding the admin_menu at the mobile screen, hence you can do 2 things:


Either inspect you site in incognito mode of Chrome or private browsing in Firefox
Permanent solution would be applying CSS for this

@media screen and (max-width: 640px) {
  #admin-menu {
    display: none;
  }
}