Integration with multisafepay

Hello,

If there is already an awnser on this forum i am sorry for that, can't find a good anwser yet.
I am trying to post my form values to a test url of miltisafepay.
At first i tried it with query string and the url https://testapi.multisafepay.com/ewx/post.php with no luck.

Then i did read about the gform_after_submission hook and now im trying to use that hook to redirect to the external site .. is this the right way? how can the redirect take place?

For now i uses the example code but it doenst redirect (probably cause it does the post in the background?):

add_action("gform_after_submission", "after_submission", 10, 2);
function after_submission($entry, $form) {
    $post_url = 'http://thirdparty.com';
    $body = array(
        'first_name' => $entry['1.3'],
        'last_name' => $entry['1.6'],
        'message' => $entry['3']
        );

    $request = new WP_Http();
    $response = $request->post($post_url, array('body' => $body));
}

Thank you in advance

I'm trying to do the same thing, has anybody found an answer yet ?