Dropdown needs scroll

Dear Menaka- can you explain further? do you know of a fix?

Hi- there are other people who have asked this- http://presscustomizr.com/support-forums/topic/last-menu-items-sub-menu-off-screen/#post-76087
however the above doesn’t work for me… I am convinced there must be a way to do it- I already have submenus- it’s actually items in a sub menu that disappear off the page. I know it will have something to do with overflow and have tried the following code with no success:
}
.tc-header .dropdown-menu {
max height:500px;
overflow-y:scroll;
}
}
@media (max-width: 979px){
.tc-header .dropdown-menu { max height:500px;
overflow-y:scroll; }
}