TALK SHIT AND GET HIT!
you're still in school man so don't put too much thought into it. in years to come fights and shit you had in school will be in the past, obviously, but also a memory that you can laugh about even with the person you were fighting with at the time. don't let him hit you first though, that fat cu
nt has a shitload of weight over you so he could do damage giving he hit you in a bad spot. try not to knock any teeth out or hit him on the side of the head near his temple or on his nose so you don't end up paying for dentistry, killing the fat prick or having to pay for his fugged up nose.
if you get him on the ground be sure to spew some derogatory slurs about his fatness. i hate fat people