Hi,

Please send your link website and screenshot some images about your problem for check and help.

Thank you

Hello,

I have solution for your issues, you can add this custom css code in your child-theme in style.css:

@media only screen and (max-width: 1200px) { 
        #menu-btn{
            display:block;
            position:relative;
            float:right;
        }                
        header{display:none;}
        header .info{display:none ;}        
        header.header-bg{background:rgba(0,0,0,1);}
        header.de_header_2{height: auto;}       
        header.transparent{background:#000000;}
        header, header.fixed {
            display:block;
            position:inherit;
            margin:0;
            padding:0;
            margin-top:0;
            height:auto ;
            background:#000000;
            padding:15px 0 15px 0;
        }
        header div#logo{
            height: 50px;
            line-height: 50px;
        }
        header.fixed div#logo {
            height: 60px;
            line-height: 60px;
            float: left;
        }
        header div#logo a img {max-height: 60px;}        
        header.fixed div#logo img{height:auto;}                
        header div#logo .logo-scroll {display: none;}                   
        nav{width:100%;}        
        #mainmenu{
            display:none;
            float:none;
            z-index:200;
            width:100%;
            margin:0;
            padding:0;
        }        
        #mainmenu ul{float: none;}
        #mainmenu a, header.header-bottom #mainmenu > li > a{
            text-align:left;
            padding-top:10px ;
            padding-bottom:10px ;
        }
        
        #mainmenu a:hover{
            background:#111 ;
        }
        
        #mainmenu > li > ul{
            visibility: visible;
            opacity: 1;
            position:inherit;
            margin:0;
            width:100%;
        }
        #mainmenu > li > ul > li > ul{
            visibility: visible;
            opacity: 1;
            position:static;
            width: 100%;
            left: 0%;
            height: auto;
        }
        #mainmenu li{
            border-bottom:solid 1px #333;
            margin:0;
            width:100%;
            display:block;
            letter-spacing:3px;
        }
        
        #mainmenu li a:after{
            display:none;
        }
        
        #mainmenu li:last-child{
            margin-bottom:30px;
        }
        
        #mainmenu li ul{
            border-top:solid 0px #333;
            top:auto;
        }
        
        #mainmenu li ul a{
            width:100%;
            background:none;
            border:none;
        }
        
        #mainmenu li ul li{
            border:none;
            padding-left: 40px ;
        }
        
        #mainmenu li ul li a{
            display:block;
            border-left:solid 1px #333;
            border-bottom:solid 1px #333;
        }
        
        #mainmenu li ul li:last-child{
            border-bottom:none;
            margin:0;
        }
        #mainmenu li ul li:last-child a{
            border-bottom:none;
        }
        #mainmenu li a{
            color:#eceff3;
        }
        
        #mainmenu  li li a{
            font-size:10px;
        }
        
        #mainmenu  li li a:hover{
            color:#fff;
        }
        #mainmenu li li li a {background: transparent;}
        #mainmenu li ul ul {left: 0;}        
        
        header.header-mobile-sticky{
            position:fixed;
        }
        
        header #mainmenu li ul li:first-child{
          border-top:solid 1px #333;
        }
        header #mainmenu li ul ul li:first-child{
            border-top:solid 0px #333;
        }
        header #mainmenu li ul ul li:last-child{
            border-bottom: solid 0px #333;
        }
        header #mainmenu li ul ul{
            border-top: solid 1px #333;
        }
        
        header #mainmenu > li > ul, 
        header #mainmenu > li > ul > li ul{
            height:0;
            overflow:hidden;
            position:static;
        }
        
        header #mainmenu li span{
            width:36px;
            height:36px;
            background:url(images/ui/arrow-down.png) center no-repeat;
            position:absolute;
            right:0px;
            top:0px;
            margin-top:10px;
            z-index:1000;
            cursor:pointer;
        }
        
        /* remove arrow for Polylang plugin */
        header #mainmenu li.lang-item span {background:transparent;}        
        header #mainmenu li span.active{background:url(images/ui/arrow-up.png) center no-repeat;}
        header #mainmenu li li span{margin-top: 2px;}        
        .smaller.header-bottom div#logo, .header-bottom div#logo {
            height: 100%;
            line-height: 60px;
            max-height: 80px;
        }       
        header #mainmenu li a span {
            width: 100%;
            height: auto;
            background: transparent;
            position: static;
            margin-top: 0px;
        }           
    }

Thank you