Cannot add sub-menu in additional menu

I’ve been having this problem since forever. I created an additional menu by inserting some codes in functions.php and header.php. It works. However, when I insert a submenu suddenly it doesn’t work.

Here’s my CSS

div.custom-menu-class ul {
padding:20px 0px 20px 0px;
list-style-type: none;
list-style: none;
list-style-image: none;
text-align:center;
    background-color:#ffd300;
    height:60px;
    margin:0px 0px 0px 0px;} 

div.custom-menu-class li {
padding: 0px 40px 0px 0px;
display: inline;} 

div.custom-menu-class a { 
color:#3d3d3d;}

div.custom-menu-class { 
color:#3d3d3d;
    height:60px;
    align-content:center;}

div.menu {
display:none;}

Here’s the link to the page http://tooedge.com/wip/mymasterjayagtdraft/canam/

Would be great if anyone can help.