What should I do about my mother who secretly got married after I spied on her, knowing that spying is forbidden, and about my usurious money that I earned from a usurious bank and my mother wants to keep?

It is not permissible to spy unless a suspicion arises to prevent an evil. Ask your mother gently and politely about her marriage, and explain to her the conditions of a lawful Islamic marriage. If you come to know that her marriage is invalid or her relationship is illicit, you are not permitted to remain silent about this evil. You must strive to change it, bearing in mind that enjoining good and forbidding evil upon one's mother is not like doing so upon others. A marriage is valid if it fulfills the lawful Islamic conditions and pillars, even if it is not documented, but documentation is important in these times. The money you obtained from the interest of usurious banks is forbidden, and you are not permitted to benefit from it except out of necessity, and your need for marriage is not among these necessities. You must dispose of this money by spending it on the welfare of Muslims, and transfer the original capital to a bank that adheres to Islamic regulations.