What is the ruling on eating lunch and accepting a chocolate gift from a company that deals with usury, and what should I do to expiate that if it is unlawful?

It is permissible to deal with companies that engage in both permissible and forbidden activities, as their money is mixed. The Prophet, peace and blessings be upon him, traded with the Jews in Medina, buying and selling, and accepted their gifts and responded to their invitations, even though he knew they dealt in usury and consumed unlawful gain. Therefore, there is no harm in having lunch or accepting gifts from such a company.