can i trust this site? how i see if the bitcoin address is real or fake?
I would say you can.
But if you don't want to trust any third party website, you can get all the information by sending a GET request to the payment URL with "Accept" equal to "application/payment-request". If you are on Linux, you can just run this:
Doing the GET-request as suggested by TryNinja is probably the safest way to get the correct address.
Under linux this can be done with one command:
curl -i -H "Accept: application/payment-request" -H "Content-Type: application/payment-request" https://bitpay.com/i/YourInvoiceID
And with
jq installed (a commandline json processor) an appealing formatted output appears when entering:
curl -i -H "Accept: application/payment-request" -H "Content-Type: application/payment-request" https://bitpay.com/i/YourInvoiceID | jq