You can't "prove" God exists. You have to have faith.
Many people have had near-death experiences where they went to Heaven or went to Hell. I believe most of those are true (but not all). If you don't believe them, I don't see what I can do.
https://www.google.com/books/edition/Modern_Day_Miracles/x25oRPC9TMkC?hl=en&gbpv=1&dq=%22I+was+in+Heaven+and+I+saw+Jesus+standing+there%22&pg=PT139&printsec=frontcover
