What is the ruling on entering into a business partnership that sells some prohibited items (alcohol and pork) if the intention of the new partner is not to benefit from these prohibited items and to allocate their profits to the other partner, while retaining only 50% of the permissible profits?

It is not permissible to participate in the trade of forbidden items such as alcohol and pork, even if mixed with permissible trade. Participation must be in what is pure only. If the partnership involves selling these forbidden items, then their price is impure and unlawful, for the Prophet, peace and blessings be upon him, said: "Indeed, Allah and His Messenger have forbidden the sale of alcohol, dead animals, pigs, and idols." One must separate from such companies that deal in forbidden things, even if it causes displeasure to parents, for the Prophet, peace and blessings be upon him, said: "Obedience is only in what is good and right." However, if the participation will only be in the permissible part, such as a gas station, and you have no connection to the restaurant or shop that sells forbidden items, then there is no objection to that. The sin of the unlawful gain falls upon your partner, and you must advise him.