顶部导航重叠垂直导航

我有一个网站，我正在为我工作的公司重新设计。这个网站和过去项目的主要区别在于，这个网站是通过一家网络印刷电子商务公司托管的，当涉及到采购和库存控制时，该公司会处理大部分后端工作。它们允许我编辑HTML内容和CSS。遗憾的是，他们没有给我任何访问权限来改变Javascript导航。我有问题的JavaScript导航重叠我的纯CSS垂直菜单下面的幻灯片。我知道这和z指数有关，但我怎么也弄不懂。有没有人有任何建议，我可以使用添加到CSS，使其停止重叠?

这里是网站，所以你可以看到发生了什么-网站

#cssmenu {
    float:left;
    position:relative;
}
#cssmenu ul {
    font-size:14px; 
}
#cssmenu ul {
    font-size:16px;
}
#cssmenu,
#cssmenu ul,
#cssmenu ul li,
#cssmenu ul li a {
  margin: 10px 0px 0px 0px;
  padding: 0;
  border: 0;
  list-style: none;
  line-height: 1;
  display: block;
  position: relative;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}
#cssmenu {
}
#cssmenu > ul {
  width: 200px;
  background: #ffffff;
}
#cssmenu > ul > li > a {
    font-family: 'PT Sans Narrow', sans-serif;
  padding: 8px 15px;
  font-size: 16px;
  color: #666666;
  font-weight: 700;
  text-decoration: none;
  -webkit-transition: color .2s ease;
  -o-transition: color .2s ease;
  -ms-transition: color .2s ease;
  transition: color .2s ease;
}
#cssmenu > ul > li:hover > a,
#cssmenu > ul > li > a:hover {
  color: #222222;
 }
#cssmenu ul li.has-sub > a::after {
  position: absolute;
  right: 15px;
  display: block;
  width: 10px;
  height: 10px;
  content: "";
  border-radius: 2px;
}
#cssmenu > ul > li.has-sub > a::after {
  top: 14px;
  background: #666666;
}
#cssmenu > ul > li.has-sub:hover > a::after,
#cssmenu > ul > li.has-sub > a:hover::after {
  background: #222222;
}
#cssmenu ul ul li.has-sub > a::after {
  top: 13px;
  background: #ffffff;
}
#cssmenu ul ul li.has-sub:hover > a::after,
#cssmenu ul ul li.has-sub > a:hover::after {
  background: #dddddd;
}
#cssmenu ul li.has-sub > a::before {
  position: absolute;
  right: 15px;
  display: block;
  width: 0;
  height: 0;
  border: 3px solid transparent;
  content: "";
  z-index:2;
}
#cssmenu > ul > li.has-sub > a::before {
  top: 16px;
  border-left-color: #ffffff;
}
#cssmenu ul ul li.has-sub > a::before {
  top: 15px;
  border-left-color: #2e353b;
}
#cssmenu ul {
    z-index:2;
  -webkit-transform:;
  transform:;
  -webkit-perspective: 600px;
  -moz-perspective: 600px;
  perspective: 600px;
  -webkit-transform-style: preserve-3d;
  -moz-transform-style: preserve-3d;
  transform-style: preserve-3d;
}
#cssmenu ul li:hover > ul {
  left: 100%;
  opacity: 1;
  -webkit-transform: rotate3d(0, 0, 0, 0);
  transform: rotate3d(0, 0, 0, 0);
  z-index:2;
}
#cssmenu ul ul {
  position: absolute;
  top: 0;
  left: -9999px;
  width: 180px;
  background: #2e353b;
  opacity: 0;
  -moz-transition: opacity 0.2s ease, -moz-transform 0.2s ease;
  -webkit-transition: opacity 0.2s ease, -webkit-transform 0.2s ease;
  -ms-transition: opacity 0.2s ease, -ms-transform 0.2s ease;
  -o-transition: opacity 0.2s ease, -o-transform 0.2s ease;
  transition: opacity .2s ease, transform .2s ease;
  -webkit-transform: rotate3d(0, 1, 0, 45deg);
  -moz-transform: rotate3d(0, 1, 0, 45deg);
  transform: rotate3d(0, 1, 0, 45deg);
  -webkit-transform-origin: left center;
  -moz-transform-origin: left center;
  transform-origin: left center;
  -webkit-backface-visibility: hidden;
  -moz-backface-visibility: hidden;
  backface-visibility: hidden;
   z-index:2;
}
#cssmenu ul li:hover > ul {
  left: 100%;
  opacity: 1;
  transform: rotate3d(0, 0, 0, 0);
  z-index:2;
  }
#cssmenu ul ul::after {
  position: absolute;
  left: -8px;
  top: 14px;
  z-index: 5;
  display: block;
  width: 0;
  height: 0;
  border: 4px solid transparent;
  border-right-color: #2e353b;
  content: "";
   z-index:2;
}
#cssmenu ul ul a {
  padding: 8px 15px;
  font-size: 12px;
  color: #ffffff;
  font-weight: 700;
  text-decoration: none;
  -webkit-transition: color .2s ease;
  -o-transition: color .2s ease;
  -ms-transition: color .2s ease;
  transition: color .2s ease;
   z-index:2;
}
#cssmenu ul ul li:hover > a,
#cssmenu ul ul li a:hover {
  color: #dddddd;
  z-index:2;
}