Hi Daniel,
Do you want the sub menu open by default on mobile? If so try this CSS:
.dropdown-click #mobile-header.main-navigation.toggled ul, .dropdown-click #mobile-header.main-navigation.toggled ul li > ul {
display: block;
opacity: 1;
visibility: visible !important;
pointer-events: auto;
height: auto;
overflow: visible;
}
#mobile-header.main-navigation.toggled .main-nav ul ul{
position: relative;
top: 0;
left: auto!important;
right: auto!important;
width: 100%;
float: none;
}