Is it permissible to buy specific goods from the market and sell them to shops outside official working hours, given that the current salary is low and there has been no response to the request for a raise?

It is permissible for an employee to engage in private business activities outside official working hours, unless the employer stipulated in the contract that the employee should not engage in private work, and the employer has a clear interest in this condition, in which case the employee must fulfill it. However, if the employer does not have a clear interest in the condition, and it is merely stubbornness, then it is not obligatory to fulfill it.