Payment Gateway redirection help

I am trying to make a new credit card payment gateway.

How can I make redirection before payment completion. What I want to do is:
– Get credit card infos from customer ( this is ok!)
– Send (post) this info to the banks website ( this is ok!)
where Banks website needs a return url, I gave this return url that the payments class file. But I couldnt process the returned data (which bank sends back).

Is there a hook or an action or a redirection process?

WP 3.9.2
WC 2.1.12
https://ww.wp.xz.cn/plugins/woocommerce/