Trying to Style Navigation..epic fail

I am trying to accomplish what this page has for styling in their navigation

http://www.soundstrue.com/store/mbsr-course

but you can see here cursoonline.mindfulness-exercises.net I am not hitting the mark..

1.) Trying to get on hover to underline the link

2.) Trying to get Purchase Now to get background color like they have.. ill use a different color, but just cant seem to get this going

I am using the Divi theme

any advice?

thanks in advance

EJ