submenu doestnt work

Hi!

Well, basically the plugin works well, but as it comes to the sub-menu,

a) the rest of the navigation doesn’t move down, so when I open the sub-menu it “overlays” the parent menu

b) the sub-menu items stay formatted in the way they are in the “regular” navigation. It seems that this is due to my overriding css, but otherwise the sub-menu isn’t formatted correctly in ghe regular nav.

c) i’m not able to close the nav once unfolded anymore

here’s the code:

header.php:

<header>
    <div id="logo"><a href="#"></a></div>
    <div class="container-responsive">
      <nav id="mainnav">

      		<?php wp_nav_menu( array( 'theme_location' => 'Mainnav' ) ); ?>

</nav>

style.css:

#mainnav {
	font-size: 1em;
	color: #ffffff;
	margin-left: auto;
	margin-right: auto;
	padding-top: .5em;
	height: 10em;
	width: 100%;
	position: relative;

}

#mainnav .menu{
	width: 536px;
	margin-left: auto;
	margin-right: auto;
	height: 55px;

}
#mainnav .menu li {
	list-style-type: none;
	float: left;
	width: 5em;
	height: 1.7em;
	background-color: #2e5363;
	border-radius: 5px;
	margin-right: .7em;
	text-align: center;
	padding-top: 3px;
	display: inline;
}

#mainnav .menu li:last-child {
	margin-right: 0;
}

#mainnav .menu li a {
	text-decoration: none;
	color: #ffffff;
	width: 100%;
	height: 100%;
	display: inline-block;
}

#mainnav .menu li a:hover {
	color: #000000;
}

.sub-menu  {
	position: absolute;

	left: -999em;
	opacity: 0;
	transition: opacity 1.5s; /* explorer 10 */
	-webkit-transition: opacity 1.5s; /* chrome & safari */
	-moz-transition: opacity 1.5s; /* firefox */
	-o-transition: opacity 1.5s; /* opera */
}
li:hover .sub-menu  {
	left: auto;
	opacity: 1;
	margin-left: -3em;
}
.sub-menu li {
	display: inline !important;
	background-color: transparent !important;
	margin-top: 10px;
	padding-top: 0px !important;
	color: #2e5363;
	opacity: 1;
}
.sub-menu li a {
	color: #2e5363 !important;
}
.sub-menu li a:hover {
	text-shadow: 0px 6px 11px;
}

thanks,

Johannes

https://www.ads-software.com/plugins/slicknav-mobile-menu/