Space and time are linked and nothing can travel faster than light, think of it as a universal speed limit.
Having a max speed can put us into strange situations, because speed is also relative.
If I’m sitting in a car watching houses go by, it seems to me like I’m staying still and the houses are going 30 mph backwards. And cars on the other side of the road seem to be going 60 mph backwards, yet they won’t get pulled over, because from the police’s point of view they are only going 30!
So what happens when two space ships going the speed of light pass by each other, as cars on different sides of the road pass by each other? Does it seem to those space ships that the other one is going twice the speed of light?