What happen to trees after it dies?

Answer 1

Trees die, and then fall down. Once on the ground, they become food for many fungi, insects, bacteria and grubs, etc in the soil.
They also rot due to constant exposure to sun, wind, and rain.
Find pictures of trees with fungus growing on them, pictures of termite-infested trees, beetle-infested trees, etc.
It is that part of nature that causes a tree to decompose.