I heard that as u approach the speed of light time slows down. what would happen if we could slow down to zero speed would time speed up and disapear in an instant?
There is no absolute fixed point to measure your speed against.
The speed of something always has to be measured relative to something else - that's why it's called relativity.
If 2 spacecraft approach each other at high speed - astronauts on each look around them and everything seems normal on board but when they look at the other time is slowed down on that one.