Hi there,
try this CSS:
#mobile-header.main-navigation ul ul {
visibility: visible;
float: none;
position: static;
height: auto;
opacity: 1;
pointer-events: auto;
}
#mobile-header.main-navigation .main-nav>ul>li>a {
background-color: #4e8abf;
color: #fff;
}
#mobile-header.main-navigation .main-nav>ul>li:hover>a,
#mobile-header.main-navigation .main-nav>ul>li.current-menu-item:hover>a {
background-color: #dd9c39;
color: #fff;
}
.mobile-header-sticky #mobile-header.toggled .main-nav>ul {
max-height: calc(100vh - 60px);
overflow-y: scroll;
}