Here is how I think this should be done. On line 362 of your confirm page you have this line of code:
$WA_redirectURL = "checkout_success.php";
I think that this line of code should be updated to go to either of the checkout success pages. You can do this with a ternary expression that would look like this:
$WA_redirectURL = (<your value for the country> == 'Deutschland')?"checkout_success.php":"checkout_success2.php";
You will just need to replace the <your value for the country> with the variable that will be holding the value of the country. Once you do this it will look at this variable, check to see if it is set to Germany, then if it is you will set the redirect to checkout success, otherwise it will be set to checkout success2. If you do it this way there will be no specail redirecting that needs to occur, we will just use the built in redirecting based on the country.