Employer Denying Sales Bonus Agreement

So basically the situation is about my father. My father was working as Senior Marketing specialist in a company and as his hardwork contributed lot of Sales to his Company. My father and his company owner signed a *Sales Bonus Agreement* stating the amount of reward which will be paid to my father in 6 months from the date of agreement made* the agreement also stated that without any issues the amount will be paid to him. As of some issue between my father and his employer, the company terminated my father without any valid reason so my father asked for his unpaid salaries and sales bonus because my father got to know that his company is trying to cheat him. For your information, we are foreigner in this country and finding job was not easy for my father due to High age issue. He requested and the company denied as they terminated my father with Labour Article 80 of Saudi Arabia saying he is not entitled for any bonus. Now my father have made case in court against the company. The company lawyer said in court that these papers are fraud not real incase the signatures are real because it have chamber of commerce authentication seal also. Now my father company lawyer have requested for forensic investigation of the documents. Please let me know what you think about this issue, if anyone requires more information pls let me know