Wordpres Woocommerce Checkout page customization

I have the latest version of Wordpress and Woocommerce. I need you to implement the following functionality. On the checkout page, below the billing and shipping data, create a new step called: "Payment Details". This is before the Payment Method step from Woocommerce. Here should be two buttons: a) Full Pay below this button display the message: Discount 10% for total price - if the user clicks on this button, recalculate the price with the discount of 10% b) Reserve / Book below this button display the message: Discount 5% for total price - if the user clicks on this button, the user will have to pay 20 euros/usd (or what currency is chosed) and there will appear a message saying that: Total amount to pay: 20 euro/usd Total remaining amount to pay: (total amount - 5% of that amount - 20 euro/usd) Example:total amount is 600 euro, the user will pay 20 euro and the message will display that the user stil have to pay the other 600 - 5% of 600 - 20 euro = 450. (5% of 600 is 30) In both cases, add a message to the email that is send to the user and admin containing information about the payment selection (a) or b)). In both cases, the mail should contain the selected payment detail and the amount information such as: how much was the total amount before the discount, after the discount, and in case of b) Reserve/Book, how much the user still have to pay. If possible, you will have to edit the file: [login to view URL] and NOT change the woocommerce plugin, because in that way I won't be able to update it in the future.