https://www.cnet.com/news/avengers-endgame-time-travel-why-it-all-makes-perfect-sense/

But it's called science fiction for a reason.

"Should be fine if we strictly follow the rules of time travel," says Scott Lang (aka Ant-Man, played by Paul Rudd) as the surviving Avengers discuss the perils of changing what once was. "No talking to your past self, no betting on sporting events." Tony Stark (aka Iron Man, played by Robert Downey Jr.) tells him that movie is "horseshit."