How to make Superfish menu vertical in first level but horizontal in second level?

Question

I use Superfish menu within Drupal7 and my first item level is designed vertical. Now I want to style my second item level horizontal. How could I do this? I tried different CSS approaches, added some class names via jQuery like

$('first-level li')find('ul').addClass('sf-vertical');

but nothing helped. tnx!

edit: here is a jsfiddle and my menu looks like

<ul id="superfish-1" class="sf-menu menu-page-menu sf-vertical sf-style-none sf-total-items-6 sf-parent-items-1 sf-single-items-5 sf-js-enabled">
    <li id="menu-622-1" class="first odd sf-item-1 sf-depth-1 sf-no-children">Item 1</li>
    <li id="menu-623-1" class="middle even sf-item-2 sf-depth-1 sf-total-children-5 sf-parent-children-0 sf-single-children-5 menuparent">Item 2
        <ul class="sf-vertical sf-hidden">
            <li id="menu-633-1" class="first odd sf-item-1 sf-depth-2 sf-no-children" style="white-space: normal; float: left; width: 100%; ">SubItem </li>
            <li id="menu-634-1" class="middle even sf-item-2 sf-depth-2 sf-no-children" style="white-space: normal; float: left; width: 100%; ">SubItem </li>
            <li id="menu-635-1" class="middle odd sf-item-3 sf-depth-2 sf-no-children" style="white-space: normal; float: left; width: 100%; ">SubItem </li>
            <li id="menu-636-1" class="middle even sf-item-4 sf-depth-2 sf-no-children" style="white-space: normal; float: left; width: 100%; ">SubItem </li>
            <li id="menu-637-1" class="last odd sf-item-5 sf-depth-2 sf-no-children" style="white-space: normal; float: left; width: 100%; ">SubItem </li>
        </ul>
    </li>
    <li id="menu-624-1" class="middle odd sf-item-3 sf-depth-1 sf-no-children">Item 3</li>
    <li id="menu-625-1" class="middle even sf-item-4 sf-depth-1 sf-no-children">Item 4</li>
    <li id="menu-626-1" class="middle odd sf-item-5 sf-depth-1 sf-no-children">Item 5</li>
    <li id="menu-627-1" class="last even sf-item-6 sf-depth-1 sf-no-children">Item 6</li>
</ul>

Answer 1

Give the fix width of .sf-menu ul li ul and .sf-menu ul ul li remove width:100% and give margin_right:XXpx;

CSS like

.sf-menu ul li ul{width:400px;}
.sf-menu ul ul li{float:left; margin-right:10px;}