we were told we can go to court, but what are our chances there???
We really can't answer that for you. Immigration court is not a game of odds and chances. Cases are handled individually, and if discrepancies are found, a denial is almost certain.

what shall we do? how to fight against such a unfairness???
How badly do you want permanent residency?

If it's something you want so badly, you can reach out and touch that desire? You hire an attorney who specializes in immigration law. Check with your local Bar Association for a referral, or with friends and community members for a recommendation.

Then follow your attorney's instructions to the letter. Best of luck to you.