Hello, I need help using PayPal Payments Pro Sandbox in the shopping cart for Website X5 Professional version. I haven't published my website online yet, but I do have a PayPal Pro account.

I enabled Sandbox test mode and used my sandbox buyer account for the checkout process. After entering my name & address, an order sent page appears prompting me to enter credit card payment details. 

I entered the payment info and then I was prompted to download a file named "pay.php". 

Could you please provide guidance for using PayPal Pro Sandbox and/or testing payment flow offline (before making site live)?

Thanks.