What is the ruling on money acquired from a 5% deposit in a savings bank that invests in building housing for young people? Is it permissible or forbidden? And what should I do with it if it is forbidden?

If the capital invested in the bank is not guaranteed, and the profit is 5% of the bank's profits, not from the capital, then the transaction is a valid Mudarabah, and the earnings are lawful. However, if the capital is guaranteed in case of loss, then the contract is a loan, and any resulting profits are usury (riba) that must be disposed of by spending them on charitable causes, along with repentance.