How much of it is true?
I was having a conversation about this question, just yesterday...
How would anyone know how much of anything was true, unless they were there for it, in person?
A responsible human needs two categories for knowledge: what is known to be true, and what is claimed as truth by others.
For myself, I accept nothing as truth unless I personally know it to be so.
Everything else is hearsay, propaganda, or lies.
And no, I didn't watch the documentary