Will god punish a very good person but doesn believes in him?
Yes. In the book of Romans is says the man’s best works, to God are but “filthy rags”. That’s actually not the best translation into English. Before the advent of the tampon, rags were used to sop up menstral flow. That’s the kind of rags that are being referenced here. Read the book of Romans. The whole point of the old testiment, laying down all the rules you have to follow to make it into heaven under your own power, was to prove that it can’t be done by sinful man. No Jesus, no heaven. It’s that simple. Bear in mind, you aren’t obeying one very important teaching of God – to accept Jesus as your savior.