Is it possible to slow down or speed time up?

Yes, it is. The theory of relativity treats time as the fourth dimension, which has a barrier as any other force. It is also stated that the time barrier can be broken if the speed of light is achieved. But there is a catch. According to the theory, to achieve the speed of light you need to have an infinite amount of energy. But, it is possible to slow down time. It is called time distortion where it is said that the closer you travel to the speed of light, the speed of time in the ship is slower compared to the speed of time outside the ship. But to travel through time, we would need to harness some energy that travels faster than light. Let’s see if tachyons (a hypothetical particle that travels faster than light) will help.