如何独立滚动侧栏中的响应式菜单

Question

这是一个我正在处理响应式菜单的问题，但问题是如果我向下滚动菜单，它会在移动分辨率

中全身滚动

这是链接here。我不知道响应式CSS，但我在谷歌上尝试过搜索过。我尝试了在Google上找到的所有职位和其他内容。

.mean-container .mean-bar { 
float: left;
width: 100%;
position: relative;
background: #0c1923;
padding: 4px 0;
min-height: 42px;
z-index: 999999;
}
.mean-container a.meanmenu-reveal {
width: 22px;
height: 22px;
padding: 13px 13px 11px 13px;
position: absolute;
top: 0;
right: 0;
cursor: pointer;
color: #fff;
text-decoration: none;
font-size: 16px;
text-indent: -9999em;
line-height: 22px;
font-size: 1px;
display: block;
font-family: Arial, Helvetica, sans-serif;
font-weight: 700;
}
.mean-container a.meanmenu-reveal span {
display: block;
background: #fff;
height: 3px;
margin-top: 3px;
}
.mean-container .mean-nav { 
float: left;
width: 100%;
background: #0c1923;
margin-top: 33px;
}
.mean-container .mean-nav ul {
padding: 0;
margin: 0;
width: 100%;
list-style-type: none;
}
.mean-container .mean-nav ul li {
position: relative;
float: left;
width: 100%;
}
.mean-container .mean-nav ul li a {
display: block;
float: left;
width: 90%;
padding: 1em 5%;
margin: 0;
text-align: left;
color: #fff;
border-bottom: 1px solid #383838;
border-bottom: 1px solid rgba(255,255,255,0.5);
text-decoration: none;
text-transform: uppercase;
}