1) Go to Theme Options > Header builder > Cart > choose the mini cart type – Off-canvas.
2) Add the Ajax add to cart for the variable products https://wordpress.org/plugins/woocommerce-ajax-add-to-cart-for-variable-products/ or https://wordpress.org/plugins/woo-ajax-add-to-cart/ to allow adding of the variable products with Ajax without page refresh and opening the mini-cart instead.
