grandfather paradox = parallel universe
It's because of the grandfather paradox that the parallel universes idea was thought of.
I like how if you travel at the speed of light (theoretically) a minute would equate to a much longer time on earth. So you could kind of fast forward into the future
Yep.
There was also a theoretical problem discovered in achieving the speed of light, as you come closer to the speed of light, you become heavier thereby adding another factor that will decrease your speed. Boring explanation, simply put, just examine Einstein's formula of E=mc(squared)