Pages dropdown menu

Hi guys!
I’m sorry if my question was already discussed somewhere here, but I haven’t found it.

I’m a total newbie in WordPress, hence, my question is absolutely “newbiesh” ??

How do I make a page-dropdown menu?
I am currently using the “Nursena” theme and my page menu it looks like this – https://alumni.pp.ua/ (in the very top of it, the “Alumni group” section).
I’ve tried to create a dropdown menu just like in the categories (“The Club” f.e.), but the result is always that one – a horizontal non-dynamic menu of subpages.

In the header I have the following code –

<div id="wrapper">
		<div id="container" class="container">
            <div class="span-24">
				<div class="span-22">
					<div id="pagemenucontainer">
						<?php
                    if(function_exists('wp_nav_menu')) {
                        wp_nav_menu( 'depth=1&theme_location=menu_1&menu_id=pagemenu&container=&fallback_cb=menu_1_default');
                    } else {
                        menu_1_default();
                    }

                    function menu_1_default()
                    {
                        ?>
                        <ul id="pagemenu">
    						<li <?php if(is_home()) { ?> class="current_page_item" <?php } ?>><a href="<?php echo get_option('home'); ?>/">Home</a></li>

<?php wp_list_pages('depth=0&exclude=0&hide_empty=0&orderby=name&show_count=0&use_desc_for_title=1&title_li='); ?>
</ul>
                        <?php
                    }
                ?>
					</div>
				</div>

Any suggestions?
I will be indescribably grateful for any assistance and advice.
Sincerely yours,
G Zuz