Custom code Woocommerce on page checkout

I have a one page checkout for one product [login to view URL] (I have multiple products on my site but I need the solution just for the product give in the url) If you check the process is like this: User select the product option->User press add to cart button->Cart is updated->Payment gateways appears->User select payment gateway and continue to payment after "pay button" I want to change this process to: Payment gateways are always visible, user select the product option ->Cart is updated automatically without press add to cart button->payment gateway is selected and user is redirected to payment gateway after "Pay button" The objective is to avoid the user press 2 buttons (Add to cart and Pay). And also payment gateways are always visible to be selected, not just after product is added to the cart. I need to achieve this and then change the layout to a custom layout.