Is an employee who has been lawfully dismissed entitled to claim his rights from the employer, especially if he has worked for him for many years and the employer has dismissed him?

It is not possible to definitively assert that you have a right against the employer except by reviewing the contract concluded between you or the labor law to which the company is committed. It may be in accordance with the Sharia or in violation of it, as is the case with some traffic and building laws drafted in the absence of Sharia.