All the css code is shown below

/*make humburger default*/
@media (max-width: 3000px){
#et_mobile_nav_menu {
display: block;
}
#top-menu {
display: none;
}
}
/*now we want the work menu shown with the hamburgwr menu*/
.mobile_menu_bar:before {
background-color: #3e4555;
padding: 2px 0px 2px 2px;
top: 9px;
color: #fff!important;}
.mobile_menu_bar::after {
font-family: Arial;
content: "MENU";
position: relative;
padding: 10px 20px 10px 5px;
background-color: #3e4555;
color: #FFFFFF!important;
cursor: pointer;}
.mobile_nav.opened .mobile_menu_bar:before {
content: "\4d";}
#main-header{padding-bottom:18px;}
@media only screen and (max-width: 980px){
.et_header_style_centered #main-header .mobile_nav {
display: block;
padding: 5px 10px;
border-radius: 5px;
background-color: #fff;
text-align: left;
}
}
.select_page { visibility: hidden; }