Dropdown Menu for Categories

Hello everyone,

I’d like to have a dropdown menu where I can see the headlines of the posts of the categories if I slide over it and can click on each to get there.

I use the theme Traction Pro. In my header.php I already got such a navigation bar but without dropdown. It says:

<div id="cat-nav" class="clear">
				<ul class="nav">
					<?php if ($traction->hideCategories() != 'true' ) : ?>
						<?php wp_list_categories( 'title_li=&exclude=' . $traction->excludedCategories()); ?>
					<?php endif; ?>
				</ul>
			</div>

It looks like this (in blue).

I read via Javascript it would be possible. Couldn’t quite manage that. But I’m also not so familiar with Javascript. Please help me. ??