It sounds like you have very little if any experience fighting.
Do not watch any particular style of martial arts, the technical aspects are too complicated to pick up in a few days. What you want to watch is MMA, specifically old pride matches. Pride did not have weight divisions so you could get tiny guys fighting massive ones. You want to go on youtube and find those fights to see how the smaller guy approached the bigger ones.
Do not try to learn any complicated moves, just stick with the basics. He has such a size advantage of you that if he gets a hold of you and brings you down the fight is over so remember that.
Give me a better idea of your sizes. How tall is he and how tall are you? I know you said hes like 240-250 but how much do you weigh? Also where do you live?
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