Hi,

1. Try to add the following code snippet to the Custom CSS area in Theme Settings to fix this issue

.main-header .vertical-navigation {
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: stretch;
      -ms-flex-align: stretch;
          align-items: stretch;
}

.main-header div.header-categories-nav-wrap {
   height:auto;
}

Please, provide us your FTP access also so we can check the 3d issue.

Thank you