DidoH

Thanks WPyogi. I will create a child theme for it. The site is http://www.wp.julialloydgeorge.com. The style.css is below

/* Small menu */
.menu-toggle {
  display: none;
  padding: 20px;
  width: 100%;
  text-align: center;
  font-family: Didot, 'Didot LT STD', 'Hoefler Text', Garamond, 'Times New Roman', serif;
  font-size: 30px;
  font-size: 1.875rem;
  font-weight: normal;
  line-height: 1.5;
  background: transparent;
  border: 0;
  color: #455353;
}
.menu-toggle:focus {
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.5);
  outline: none;
}

/* =Responsive
----------------------------------------------- */
@media screen and (min-width: 500px) {

	.main-navigation .mobile-menu {
		display: none;
	}

}

@media screen and (max-width: 1000px) {
  body.blog .entry-title:after,
  body.archive .entry-title:after {
    content: ' \203A';
  }
  body.blog .entry-excerpt,
  body.archive .entry-excerpt {
    display: none;
  }
}
@media screen and (max-width: 800px) {
  body.single .hentry,
  body.page .hentry,
  body.search-results .site-main,
  body.search-no-results .site-main,
  body.error404 .site-main,
  .comments-area,
  .single .navigation,
  .page .navigation {
    margin-right: 40px;
    margin-left: 40px;
  }
}
@media screen and (max-width: 700px) {
  body.blog .no-image:before,
  body.archive .no-image:before {
    padding-top: 0;
  }
  body.blog .no-image .post-link,
  body.archive .no-image .post-link,
  body.blog .no-image .entry-header,
  body.archive .no-image .entry-header {
    position: relative;
    top: auto;
    left: auto;
    bottom: auto;
    right: auto;
  }
}
@media screen and (max-width: 500px) {
  body.single .hentry,
  body.page .hentry,
  body.search-results .site-main,
  body.search-no-results .site-main,
  body.error404 .site-main,
  .comments-area,
  .single .navigation,
  .page .navigation {
    margin-right: 0px;
    margin-left: 0px;
  }

  main-navigation .primary-menu,
  main-navigation .secondary-menu,
  main-navigation .social-menu {
    display: none;
  }

  .main-navigation .mobile-menu {
    display: block;
  } 

  body.blog .with-image:hover .entry-header,
  body.archive .with-image:hover .entry-header {
    opacity: 0;
  }
  .entry-title {
    font-size: 22px;
    font-size: 1.375rem;
  }
  .entry-excerpt,
  .read-more {
    display: none !important;
  }
  .comment ul.children {
    margin-left: 10px;
  }
  .two-column .sidebar {
    float: none;
    width: 100%;
  }
}
@media screen and (max-width: 400px) {
  .site-content,
  .secondary-content {
    padding-right: 20px;
    padding-left: 20px;
  }
  body.blog .hentry,
  body.archive .hentry {
    margin-top: 20px;
    margin-bottom: 20px;
    width: calc(50% - 10px);
  }
  body.blog .hentry .entry-header,
  body.archive .hentry .entry-header {
    padding: 10px;
  }
  .alignright,
  .alignleft {
    display: block;
    float: none;
    width: 100% !important;
    margin-left: 0;
    margin-right: 0;
  }
  .entry-meta .entry-author {
    margin-bottom: 10px;
  }
  .entry-meta .entry-author,
  .entry-meta .entry-taxes {
    display: block;
    float: none;
    max-width: 100%;
    text-align: left;
  }
  .entry-meta .entry-categories,
  .entry-meta .entry-tags {
    display: block;
    margin-bottom: 10px;
  }
  .entry-meta .entry-categories .genericon,
  .entry-meta .entry-tags .genericon {
    margin-left: 0;
  }
  .comments-title,
  .comment-reply-title {
    font-size: 22px;
    font-size: 1.375rem;
  }
}

This is the functions.php. I have created the secondary and the mobile menu and moved the secondary and social menu to a different location to the primary menu.

// This theme uses wp_nav_menu() in one location.
	register_nav_menus( array(
		'primary' => __( 'Primary Menu', 'museum' ),
		'social'  => __( 'Social Links', 'museum' ),
		'secondary' => __( 'Secondary Menu', 'museum' ),
        'mobile' => __( 'Mobile Menu', 'museum' ),
	) );