I read this novel like a couple years ago (probably 4-5 years already). It's kinda old I guess and my detail maybe is not very specific but I try my best.
The story is talk about a young boy (Maybe the age around 14-16 like this.) trying to survive in a jungle and it end up living in the jungle for a couple years in there. The novel I recall it has 5 volume, it has different ending too.
The story start like this, the young boy ride his uncle small airplane across a jungle but end up his uncle suddenly have heart attack and crash on the lake. (Actually not sure is the uncle have heart attack or the plane have engine problem.) The young boy manage to escape but unfortunately his uncle passed away from the heart attack.
It has 2 different storyline I remember:
The first one is after surviving in the jungle for like almost a year. The young boy finally got rescue and return back to his normal life but after living a couple month in the city, he feel that he doesn't like that life, he want to go back to the jungle to relax. So he when back again to the jungle and the story continue.
The another ending is the young boy did not rescue by the people but his second challenge is coming near, he need to survive the winter period. I remember before he face the winter, he went back to the crash site (the airplane crash into the lake that part) and search for some equipment. I remember he found a gun in that plane and some more better equipment to help him hunting.