WP Theme Best Minimalist Menu overlapped with Page/Post image

How to always make the toggled menu appear over any post or page images?

enter image description here

/*————————————————————–

Menus

————————————————————–*/
.main-navigation {
display: block;
clear: none;
}

.main-navigation ul {
list-style: none;
margin: 0;
padding: 0 1.5em;
text-align: right;
}

/* Hide the menu on small screens when JavaScript is available. * It only works with JavaScript. */

.js .main-navigation ul,
.main-navigation .menu-item-has-children>a>.icon,
.main-navigation .page_item_has_children>a>.icon,
.main-navigation ul a>.icon {
display: none;
}

.main-navigation>div>ul {
border-top: 1px solid #eee;
padding: 0.75em 1.695em;
}

.js .main-navigation.toggled-on>div>ul {
display: block;
}

.main-navigation ul ul {
padding: 0 0 0 1.5em;
position: relative;
box-shadow: 1px 1px 1px rgba(0, 0, 0, 0);
top: 0;
}

.main-navigation ul li:hover>ul.toggled-on {
display: block;
float: none;
left: 0;
}

.main-navigation ul ul a {
padding: 0.4em 0;
position: relative;
text-transform: none;
}

.main-navigation li {
border-bottom: 1px solid #eee;
position: relative;
float: none;
}

.main-navigation li li,
.main-navigation li:last-child {
border: 0;
}

.main-navigation a {
display: block;
padding: 1em 0;
text-decoration: none;
color: #222;
}

.main-navigation a:hover {
color:#ff22c0;
}

.main-navigation li a,
.main-navigation li>ul a {
font-weight: 600;
text-transform: capitalize;
}

.site-header.custom-active.nav-down.topmost .main-navigation ul ul {
background: transparent;
background: rgba(0, 0, 0, 0);
}

.site-header.custom-active.nav-down.topmost .main-navigation ul ul a {
background: transparent;
background: rgba(0, 0, 0, 0);
}

.site-header.custom-active.nav-down.topmost .main-navigation li li:hover,
.site-header.custom-active.nav-down.topmost .main-navigation li li:focus {
background: transparent;
background: rgba(0, 0, 0, 0);
}

.site-header.custom-active.nav-down.topmost .main-navigation li li {
border: 1px solid #ffffff26;
}

.site-header.custom-active.nav-down.topmost .main-navigation li li:last-child {
border-top: 0;
}

/* Icon Navigation */

i,
i:before,
.main-navigation li a {
-webkit-transition: all 0.3s ease-in-out;
-moz-transition: all 0.3s ease-in-out;
-ms-transition: all 0.3s ease-in-out;
-o-transition: all 0.3s ease-in-out;
transition: all 0.3s ease-in-out;
}

.main-navigation li:hover i::before {
display: inline-block;
-webkit-transform: rotate(0deg);
-moz-transform: rotate(0deg);
-o-transform: rotate(0deg);
-ms-transform: rotate(0deg);
transform: rotate(0deg);
}

/* Menu toggle */

.menu-toggle {
background-color: transparent;
border: 0;
-webkit-box-shadow: none;
box-shadow: none;
color: #222;
font-size: 14px;
font-size: 0.875rem;
font-weight: 800;
line-height: 1.5;
margin: 0;
padding: 1em;
text-shadow: none;
display: none;
}

.main-navigation .desktop-dropdownsymbol {
display: none;
font-size: 9px;
}

/* Display the menu toggle when JavaScript is available. */

.js .menu-toggle {
display: block;
}

.main-navigation.toggled-on ul.nav-menu {
display: block;
}

.menu-toggle:hover,
.menu-toggle:focus {
background-color: transparent;
-webkit-box-shadow: none;
box-shadow: none;
color: #ff22c0;
font-weight: 400;
}

.menu-toggle:focus {
outline: none;
}

.menu-toggle .icon {
margin-right: 0.5em;
top: -2px;
}

.toggled-on .menu-toggle .icon-bars,
.menu-toggle .icon-close {
display: none;
}

.toggled-on .menu-toggle .icon-close {
display: inline-block;
}

/* Dropdown Toggle */

.dropdown-toggle {
background-color: transparent;
border: 0;
-webkit-box-shadow: none;
box-shadow: none;
color: #222;
display: none;
font-size: 16px;
right: -0.5em;
line-height: 1;
margin: 0 auto;
padding: 1.2em 0.5em 0;
position: absolute;
text-shadow: none;
top: 0;
}

.dropdown-toggle:hover,
.dropdown-toggle:focus {
background: transparent;
color: #ff22c0;
}

.dropdown-toggle:focus {
outline: thin dotted;
}

.dropdown-toggle.toggled-on .icon {
-ms-transform: rotate(-180deg);
/* IE 9 /
-webkit-transform: rotate(-180deg);
/
Chrome, Safari, Opera */
transform: rotate(-180deg);
}

.main-navigation li.search a span {
display: none;
}