You cannot travel in time because there is no such thing as time. We are a constantly changing. To travel back in time would mean to change everything to exactly the way it was at that point in the past. Even then you would not technically be travelling in time. You would just be changing everything.

Example: If you changed the entire universe back to the way it was 10 years ago with your current self being there then you could say you went back in time in a sense. There would also be a new outcome of events with you there.

If there is any form of time travel it means controlling the entire universe atom by atom.

Again, my point is there is no such thing as time. We just exist in an ever evolving universe.