Luckily, as far as we understand things, there's no way to go back in time (only less fast to the future, which isn't the same). For one thing, because there's no backup mechanism for reality to jump back to.
Timelines are fiction. They hurt some fundamental principles of how the universe works. Time isn't like a river or a line at all; better start thinking of time like the air around you: it's just there, can be formed, affects things but there can't be less than none.