Magento Shop modification

I have a Magento 1.X. Shop. I am using [login to view URL] for for the payment method bank transfer. 1. When someone buys through the shop via bank transfer, Komfortkasse sends an email to customers with the payment information. Komfortkasse offers a Magento plugin. However, I would like to have the payment information displayed additionally on the success page of all bank transfer customers. You have to use their API for that. The API can be found at: [login to view URL] The transfer information on the success page should, of course, only be displayed for bank transfer customers. Not for all other customers. In addition, the customer should be able to print the information on the succcess page. 2. Using the payment possibility "bank transfer" in our shop, we can not be sure whether the customer will pay or not. We would like that the customer has the possibility to pre-mark the payment after making the bank transfer by using a button. This is an easy way to give us the information of finished payments. For this customers the status of an order should be change for example to banktransfer_advance after pushing the button. For that solution we need a button on the success page and in the login area for all bank transfer customers. All the information about the possibility of using such a button should be included automatically in the welcome e-mail of our shop, but only for customers using the payment option "bank transfer". We want to motivate the customer doing the transfer quickly and informing us easier about the payment for a faster shipping.