[Fixed]-Category matching query does not exist. I don't understand why it's sending me to wrong url

The reason it is doing this has nothing to do with django, but rather because you have relative links in your template.

If you are already at a link http://localhost/foo, and you place a link such as <a href="bar/zoo">link</a>, then the resulting URL will be http://localhost/foo/bar/zoo, and not http://localhost/bar/zoo.

You need to adjust your template so that you are using absolute links.