I have a big problem regarding my studies and my family ?

If you ask me your parents are being very childish! Seriously, so what if you didn't get a great grade? You passed it! That should be all that matters right? and about the competition, thats all it was, a competition, just a bit of fun. Your parents say that they are ashamed of you, they must be joking, because a parent should NEVER be ashamed of their offspring just because they didn't get a brilliant grade! They seriously need to grow up and act their age. Don't worry, they will see sense and ask you to forgive them , trust me.