Only when you die can you know for sure whether heaven or hell is real. However, we believe it or not based on our personal convictions that have been framed by religion and spirituality. If you believe in God, then you'd believe that heaven and hell is real. There's a resting place for everyone and good people will certainly not be with bad people. They are placed above them. They don't get equal judgement.
Logically, Looking at all the evil going on around the world today, evil doers are literally going Scott free, you'll know that it isn't what nature intended. Naturally, people pay for all the bad things they've done. So if they go free here, they are walking straight into the here after to pay for their sins and the innocent ones will be duely comforted. That's just how it is and no one can escape retribution.