How can the mistake of my younger brother be rectified, who took 700 riyals from our father's card, bought items online with it at double the price, then spent the money, and how can his subscription to a foreign movie website be handled and transformed into a profitable business?

Your brother must return the money he took from his father’s card or seek his father’s forgiveness for it. As for the profit from selling a permissible item that he bought with his father’s money without permission, there is a difference of opinion among scholars, and the preponderant view is that it should be divided between him and his father. As for earning money from foreign movie and series websites, it is not permissible due to their inclusion of prohibited content. He must dispose of this money by spending it on charitable causes and public welfare. He must also be advised to repent, seek out what is lawful, and adhere to the regulations of Islamic law.