HI,

you need

1) Find function thegem_before_nav_menu_callback() line 2284 in file functions.php (screen 1118)

2) use following css:

#primary-navigation .menu-toggle {
    font-size: 15px !important;
    line-height: 15px;
    color: #fff;
    text-align: right;
    text-indent: initial;
}
#primary-navigation .menu-toggle  span{
    display:none !important;
}