Help me with a hardcoded 'drop down category menu'

This is my site http://test99.info/ and i want to make a drop down menu for the top menu (where the categories are Dogs, Cats, etc). I tried changing the ‘wp_list_categories’ to “wp_dropdown_categories”. But what that did was make the lower navigation bar a dropped menu instead of the top. I tried to understand how to code the drop down menu but its too hard for me to understand. So if someone could please help me with it i’d really appreciate it. So heres my header.php and style.css if u need to see that.

header.php

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