Convert here I have a question

I put a similar post on earlier in the week about trying to give dawah to my parents and I've ran into a bit of problem so here's my question.

How can I trust man ?

I know the quran is revelation from God but its been nearly 1500 years since prophet muhammad pbuh, how can we trust humans when we are so corrupted ? people say history is only written by the winners, and leaders change things to suit their narrative or to better them so how we do know the same thing doesnt apply to the holy quran ?