Is trading in the currency market (forex) permissible, especially when borrowing euros and selling them, anticipating a fall in the dollar's price, then repurchasing them after the drop to repay the loan and make a profit, taking into consideration that the borrowing process is done electronically or through a broker?

It is permissible to trade currencies through Forex if the prohibitions are avoided and the Shariah controls for currency exchange are adhered to. Benefiting from changes in exchange rates is not a reason for prohibition. However, if the lending broker stipulates to the borrower that their trading must be through them, the transaction becomes forbidden.