Editing Header Links

Website:
http://www.trash.abbatu.org/

I want to edit the header dropdown links because they do not display correctly. When clicking on “By Product” is displays:

http://www.trash.abbatu.org/?post_type=product

the footer is set correctly:
When clicking By Product it displays this page:
http://www.trash.abbatu.org/?product_cat=by-product

Where can i edit this? is there a easy way to fix this?

Thank you in advance