Xd alright I can go explain this the hard way then. Are you familiar with the terms length contraction and time dilation? Due to this effect time slows in moving objects. there is only one way I know to explain this fairly easy.
picture a car moving at 100m/h to the east. then it decides to go north-east. Even though the car is still moving at 100m/h it is going less then 100m/h into the east direction because some of it's energy is used to go north as well. Replace north with space and east with time and you will see that if you start moving you will start moving faster in space but slower in time. due to this effect light is measured at the same speed by all objects. no matter what speed they may have. if you would go 100% north (travel in space) time would stand still. this speed is c


