What is the ruling on bank fees for a loan, and are they considered usury? What is the ruling on being ignorant of the prohibition of giving usury? Is expiation obligatory for that? Is the purchased land considered lawful or unlawful after repaying the loan with its fees? Does the same ruling apply to credit cards?

The fees that usurious banks charge on loans are usurious interest, which is forbidden for both parties. If you were unaware that the sin of usury includes both the taker and the giver, then there is no sin upon you for engaging in usury. However, you incur the sin of neglecting the obligatory learning. You and your partner must repent to Allah. If selling the land enables you to repay the loan and free yourselves from usurious interest or reduce it, then that is obligatory. Otherwise, you are not obligated to sell it, and you may benefit from it as you wish.