In fact, it's easier than it seems. When
When gravity affects an object, his space-time is being curved by the mass of the one who provocates gravity. So, if time and space are being curved, the distance the object has to travel is longer, so it's his time. In
In conclusion, mass curve space-time, and, by curving space time, time appears, and last longer. I hope this wi'llwill be helpful.