Why does the student surpass his master?
This phrase comes from the buddhism belief that once a student has learned all there is to learn, then they will not need the teachings of the teacher.
Can a student surpass a teacher?
There is no student who can ever surpass the teacher.
What does student becomes the master mean?
It means the person who was learning something has become very very good at that thing, so good that they are probably better than their teacher. You can use this phrase when you do something better than the person who was supposed to be better than you.
What does Poor is the pupil who does not surpass his master mean?
The expression might mean that a good pupil/student should learn everything that the master/teacher knows and then learn more. If the student learns more than the master, then the student can become a master and the new students will learn more than the previous generation, and the world will have more knowledge.