Media Queries for Tablet - Nav Button

Site URL: http://https%3Adivine.cymru

Looking for help with CSS for Media Queries on viewing with tablets.

I'm very happy with my site on both Mobile & Desktop. There's just some difficulty getting my sight to look good in between. Weather it's a desktop with a narrower window or a tablet viewing my page, my navigation and buttons in the header are all over the place. I'd like code to change how my button looks like in Tablet viewing. Both examples are below for comparison.

I think I sent code in another question or on SS group on Facebook...

Have you solved yet?