Hello Spiros,
To achieve curtain menu feat you have to add CSS in additional CSS section, To go to additional CSS, first open you dashboard and from there go to Appearance >> Customizer, you will find additional CSS section and paste the following CSS
@media screen and (max-width: 576px) {
.site-header-menu {
display: -webkit-box;
display: -ms-flexbox;
display: flex;
-webkit-box-orient: vertical;
-webkit-box-direction: normal;
-ms-flex-direction: column;
flex-direction: column;
margin-top: 0;
-webkit-transform: translateX(-100%);
-ms-transform: translateX(-100%);
transform: translateX(-100%);
position: absolute;
top: 100%;
left: 0;
-webkit-transition: 0.5s ease-in-out;
-o-transition: 0.5s ease-in-out;
transition: 0.5s ease-in-out;
z-index: 9999;
background: #fff;
width: 100%;
padding: 25px;
}
.site-header-menu.toggled-on {
display: -webkit-box;
display: -ms-flexbox;
display: flex;
-webkit-transform: translateX(0);
-ms-transform: translateX(0);
transform: translateX(0);
}
.main-navigation {
height: 80vh;
overflow-y: auto;
scrollbar-width: none;
}
.site-header-menu.toggled-on {
position: absolute;
}
}
Hope it work as per your need.
Sincerely,
Minal