Writing letters..HelP!!! idk?

so i'm writing a letter to my great uncle who's in prison for something he didn't do, and now he has to stay in there until they decide if he'll have another trial and they don't even go to court to decide that until may....soo i'm writing him letters. now we were never very close i don't think, but i didn't realize how much i care for him until this happened, maybe it's just the emotion it's brought on our family that makes me feel that way, but i still want to talk to him anyway. i've written 2 letters a couple weeks ago and they were both pretty short. i just told him how i love him, missed him, and how i knew he'd get out in may blah blah blah...it all sounded so naive, but for some reason (for once) i couldn't think of anything to say! he replied and i got his letter yesterday...he told me EvErYtHiNg a/b everything...he filled up a whole page and a half...i think that's probably almost as many words then we talk to each other in 6 months time! but anyway i can't think of anything to say back to him other than commenting on what he said. idk what to tell him a/b my life...i'm 15 so idk. i mean i could tell him a/b my speech that i'm doing, how i had fun doing something...but idt he would be interested in that....can anyone think of something i could say?? and i'm sure he wants to know some a/b me too but idk what to say.. i know this is rediculous sounding to ask this on here...but every time i want to write, i go blank...i'm not usually like this. but anyways whoever helps me the most gets automatic best answer :) and you'll all get thumbs up if it helps at all :)