Added to cart error

Hello team,
I installed the plugin and it’s not working as in the demo.
On the product backend page, I have added the 2 products in the frequently brought together section. I have selected layout-2 but it not display on the product page that’s why I used the shortcode for that. It displays but it’s not working properly, 2) when unchecking any product from brought together section in add to cart button the will not change. 2) When added to the cart the main product will add two times to the cart.

Thanks.

The page I need help with: [log in to see the link]