Hey guys can someone help me i just got fucked badly by a person i sold him a site for $300 pushed the domain to him to his yahoo email and the payment went as reserved is there a way to hack his ymail so i can get my domain back i"ll be paying if someone can do this.

If you have read the Hacking & Cracking ^Rules you'd know there will be no discussions about these subjects in the forums.
Second you are asking ppl to commit a crime for you offering them money to do so?