I'm not super familiar with all the Biblical rules, but here are some of which I know that we no longer follow: A woman must marry her rapist, you cannot wear a cloth of multiple materials, you have to grow a beard (if you're a man), avoid women on their period and anything on which they sat during that time, "Any person who curseth his father or mother must be killed," "If a man has love with a woman on her period, they are both to be cut off from their people," "People who have flat noses, or are blind or lame, cannot go to an altar of God," "Anyone who dreams or prophesizes anything that is against God, or anyone who tries to turn you from God, is to be put to death," "Entrance into the assembly of the Lord was granted only to those with complete testicles," "False prophets are to be killed by their own parents."
I don't understand what you mean by "I do not believe in gay marriage." It obviously exists, lol.