Is the debtor obligated to repay only 5 million to the bank after the bank waived half the debt and restructured the original amount of 10 million, or should he repay the full amount after recovering it from the fraudsters?

The two individuals committed a great sin by borrowing from a usurious bank and by lying and forging documents to obtain the loan. They must repent, show remorse, and resolve never to return to such an act. As for the agreement reached between the bank and the debtor's agent to waive half of the debt after the bank became aware of the truth, it is valid. The creditor has no right to demand from the debtor what he has waived or absolved him from, and the debtor is not obligated to return what the creditor waived after he becomes solvent, because what is relinquished does not return.