I need help making a chat based trade system that trades the item that is in your mainhand

i basically need help making it when you click on a players name in the list i made it starts a trade with that person also not to mention getting the item in your main hand and removing it in your inv and giving it to the other person i would like for it so theres text that updates based on what you have in your mainhand and its sent to the person your trading with and when there happy with it making a /trigger taccept ik how to make a /trigger command it to link up to the trading items function