,,what should you do if you bestfriend betrayed you,,will you forgive him?

First of all remove the adjective'best' while referring to this friend. While a good friend cannot resort to cheap behaviour, the term'best' no longer fits this friend of yours. Let him just be an ordinary friend of yours and demote his status. If he is unhappy about it, let him come and ask, and then you can once again give him the privileged title. You can then tell him that you are unhappy and displeased with him. Another course of action would be to straightaway confront him with his stupid behaviour and tell him that you cannot consider him to be your best friend any longer. But, to cut a long story short, the moral remains-he is NOT your'best' friend.