Hello!
Do you have the complete documentation of your payment gateway, provided by the bank? This is a must in order for anyone to complete this project. I would be able to make it work within 3 days, as stated in my bid, provided you can send the docs right away or have access to them. There should also be some test account or sandbox set up by the bank, I guess, and once the sandbox tests are fine, they'll put you in live mode, that's pretty much a standard procedure with most of the banks.
Regards,
Dragos