To make menu transparent, please add the following css to Customizer> Custom code> Custom css:
.noo-header {
background-color: #FFFFFF ;
width: 100%;
/* top: 0; */
position: absolute;
}
.navbar {
border-bottom: 1px solid #f2f2f2 ;
width: 100%;
background-color: rgba(255,255,255,0.5);
border: 1px solid rgba(255,255,255,0.5);
}
.navbar-fixed-top {
background-color: #ffffff !important;
}

Note: When you scroll the menu down and want it to be transparent, please remove this CSS:
.navbar-fixed-top {
background-color: #ffffff !important;
}