In our culture, people believe when they died, they will getbe reincarnationed.

That means you will be reborn as an another person or maybe an another species, like an animal.

"Born" is grammatical, but "reborn" makes more sense here.

When the first time I knewheard that, I was thinking that I would like to be a big tree if I canould choose the next life.

"Know" implies a continued state, so it doesn't make sense to talk about a "first time."

A tree that never moves, doesn'tno matter how the environment changes.

A tree that is always stable, kind and reliable.