Using 2 different fully Functional themes within WordPress

I want to use two themes within wordpress, the problem is I’m able to use theme number two but it still performs like theme number 1. I want the themes to function Independently of each other. For instance one theme is my site theme while I have another theme that must act like my storefront. Now when I use the second theme, it still reacts like theme one?

Do I have to create a subdomain , download wordpress again and redirect the shopping page through a link, or does anyone know of an easier way to accomplish this ?