Problem when adding item in cart

I select item, add it to cart, after I must deselect all because the previous item added to cart is yet selected, I select another item, click on Add to cart and the message “Your item is added to cart” appear always, it is really confusing.
And sometimes, I have one item selected and when I add to cart, the popup for adding item in the cart say 2 items selected. I think it have a problem with this function.