My friend sent me a gift card email but I didn't get it
Now as some people may say resend it or make him check the purchase history none worked
It is still April 25th here. Perhaps it has yet to be processed.
Here is the information on resending gifts anyway: Resend iTunes Gifts - Apple Support.
If it was sent to the correct email address then perhaps the message has been intercepted by a spam filter.
It is was sent to the wrong address, but the address exists, then someone else may have redeemed the gift already.
If those images are supposed to be proof that payment was sent for something you're sending in return, then wait until you've received the gift voucher and redeemed it to your account. I may be doing your friend a disservice, but that are scams involving iTunes credit and it is best to be cautious.
tt2