Thank you for helping me out. I like the idea of having a success page in each language. I can redirect to each page, because the confirm page is set up with include files for each language.
I am having problems though setting the page to go to a certain success page. Right now the form action is set to: <?php echo $_SERVER["PHP_SELF"]; ?>
I am not really familiar with php. Can I just set action to checkout_success.php? And then for the other languages checkout_success_e.php, checkout_success_f.php and checkout_success_s.php?