Is an employer entitled to prevent employees from working overtime outside the establishment, and should leave be paid if employees work during it?

The agreed-upon conditions and salaries in the contract must be fulfilled, based on the words of Allah Almighty: (O you who have believed, fulfill [your] contracts) and the words of the Prophet, peace be upon him: "Muslims are bound by their conditions." There is no harm in requesting a salary increase or paid leave, and the employer has the freedom to accept or reject.