What is the ruling on buying dollars from Libya and selling them in Egypt, then buying Libyan currency from Egypt? And are the profits resulting from this operation lawful? And how should one dispose of previous profits if the act was unlawful?

It is permissible to trade currencies, provided that the Sharia (definition) conditions for exchange are met, which is the immediate possession (qabḍ) in the session of the contract. If the sale is concluded with immediate possession, then the earned money is halal (definition) (permissible). However, if immediate possession does not occur, and the delivery of both counter-values or one of them is delayed, then the profit resulting from these transactions is usury (riba) and must be disposed of. Immediate possession occurs when each of the contracting parties delivers what is due to the other into their hand or bank account before the session concludes.