Time travel

I genuinely believe in time travel, aliens, zombies, ghost and shit like that but when I watched Donnie Darko and Re-Animator for the first time in 2013 I absolutely 100% knew that time travel was possible. Those two movies shaped my personality and way of life entirely. Like right now I’m wondering if time travel exists then why isn’t anyone from the future coming to say hi or to meet their past selves. Then it hit me. They probably all have at least seen back to the future or any time travel move that if you meet your self in the future or past or if you at least touch or move something in the past or future it can fuck up the space and time balance. Hence forth why nobody has came from the future cause if the do then one wrong move they would have never existed.