Click the menu does not work on mobile

Question

I made a responsive menu that in the browser works, but on smartphone I cannot click on the child link. Example user menu --> create. When I click user it opens the options (list, create and change the password), however, when I click on any of the links the menu closes.

#nav > a {
    display: none;
}
#nav li a {
    display: block;
}
#nav li a:active {
    background-color: !important;
}

/* first level */
#nav > ul {
    background-color: #2d2d2d;
}
#nav > ul > li > a {
    line-height: 2.5em; /* 60 (24) */
    text-align: center;
}
#nav > ul > li:hover > a,
#nav > ul:not( :hover ) > li.active > a {
    background-color: #2d2d2d;
}

/* second level */
#nav li ul {
    background-color: #2d2d2d;
    display: none;
    position: absolute;
    top: 100%;
}
#nav li:hover ul {
    display: block;
    left: 0;
    right: 0;
}
#nav li:not( :first-child ):hover ul {
    left: -1px;
}
#nav li ul a {
    border-top: 1px solid white;
    padding: 0.75em; /* 15 (20) */
    color: white;
}
#nav li ul li a:hover,
#nav li ul:not( :hover ) li.active a {
    background-color: #e15a1f;
    color: #335a9e;
}

@@media only screen and ( max-width: 62.5em ) /* 1000 */ {
    #nav; {
        width: 100%;
        position: static;
        margin: 0;
    }
}

@@media only screen and ( max-width: 40em ) /* 640 */ {
    #nav; {
        position: relative;
        top: auto;
        left: auto;
    }
    #nav > a {
        width: 3.125em; /* 50 */
        height: 3.125em; /* 50 */
        text-align: left;
        text-indent: -9999px;
        /*background-color: #e15a1f;*/ /* Simbolo do menu */
        position: relative;
    }
    #nav > a:before,
    #nav > a:after {
        position: absolute;
        border: 2px solid #fff;
        top: 35%;
        left: 25%;
        right: 25%;
        content: '';
    }
    #nav > a:after {
        top: 60%;
    }
    #nav:not( :target ) > a:first-of-type,
    #nav:target > a:last-of-type {
        display: block;
    }

    /* first level */
    #nav > ul {
        height: auto;
        display: none;
        position: absolute;
        left: 0;
        right: 0;
    }
    #nav:target > ul {
        display: block;
    }
    #nav > ul > li {
        width: 100%;
        float: none;
    }
    #nav > ul > li > a {
        height: auto;
        text-align: left;
        padding: 0 0.833em; /* 20 (24) */
    }
    #nav > ul > li:not( :last-child ) > a {
        border-right: none;
        border-bottom: 1px solid /*#cc470d*/; /*Linha que separa os menus*/
    }

    /* second level */
    #nav li ul {
        position: static;
        padding: 1.25em; /* 20 */
        padding-top: 0;
    }
}

<header>
    <div class="container">
        <nav id="nav" role="navigation" class="navbar navbar-inverse navbar-fixed-top">
            <a href="#nav" title="Show navigation">Show navigation</a>
            <a href="#" title="Hide navigation">Hide navigation</a>
            <ul class="nav pull-left">
                <li class="navbar-text pull-left">
                    <a href="#" class="dropdown-toggle" data-toggle="dropdown">Usuário<b class="caret"></b></a>
                    <ul class="dropdown-menu">
                        @if (Administrador)
                        {
                        <li>@Html.ActionLink("Listar", "Index", "Usuario")</li>

                        <li>@Html.ActionLink("Criar", "Criar", "Usuario")</li>
                        }
                    <li>@Html.ActionLink("Alterar Senha", "AlterarSenha", "Usuario")</li>
                </ul>
            </li>
        </nav>
    </div>
</header>

How can I change this code so that clicking the menu item works on the smartphone?

Thank you