What is the amount I am obligated to repay my friend: is it the value of the sum on the day I left my country, or its value on the day of repayment, knowing that the local currency has depreciated? And what is my ruling if Allah causes me to die before repayment, knowing my sincere intention to repay?

If the borrower did not lose the amount in trade and knows that it is a debt that must be repaid, then the debt must be settled with the equivalent of what was established at the time it was incurred. This is not tied to price levels, inflation, gold, or silver, as long as the currency of the debt remains, unless there is an exorbitant exploitation that clearly amounts to injustice against the creditor.

As for one who dies owing a debt, intending to repay it, but leaves no sufficient wealth for it, and did not neglect its repayment during his lifetime, then he falls under the saying of the Prophet, peace and blessings be upon him: "Whoever takes the money of the people with the intention of repaying it, Allah will repay it on his behalf. And whoever takes it with the intention of destroying it, Allah will destroy him." It appears that there will be no accountability for him in the Hereafter; rather, Allah will take care of it on behalf of the creditor.