Is it permissible for an employee to take the difference in the price of shares that his company sold to him in America, knowing that the company deals with usury and speculates in the shares of other companies that may deal in prohibited things?

This transaction is considered a brokerage. Scholars have differed regarding the ruling on brokerage, with some prohibiting it due to uncertainty (jahalah) in the fee, and others permitting it based on the narration from Ibn Abbas. It is advisable to avoid these dubious transactions, in accordance with the Prophet's sayings: "Leave what makes you doubt for what does not make you doubt," and "Whoever guards himself against doubtful things, he has indeed protected his religion and his honor." For the ownership of company shares and trading in them to be permissible, it is stipulated that the company's activity must be lawful and that it does not deal with interest (riba).