Time travel is relatively IMPOSSIBLE. Travelling at light speed requires a lot of energy and it only causes time to stop. To control time? Time is not individual.
Travelling back in time is impossible. Travelling forth? You practically cannot. This is due to the fact that you cannot barge forth into time. You can't slow your speed to that level. As a matter of fact, you are time-travelling now. But, it is so slow, you think it is normal. You can stop time? No. You can speed up time? Y-yes. But, it does not make sense. Time does not judge events. So, you can't make concrete predictions on the events if ever we were to time-travel.