Is it permissible for me to invest my personal money in the company I work for to benefit from its profits, and contribute to the rent, taxes, and workers' rights, and give them a portion of my profits, while concealing the matter from them for fear of their refusal to increase it, knowing that I am diligent in my work?

It is not permissible for an employee to invest her private funds in the company's business without the employer's permission, because the employee's hand is a hand of trust, and she is an agent for the employer. She cannot act outside the bounds of the agency. An agent has no authority to dispose of anything except what is necessitated by the express or customary permission of her principal. A company contract is a commutative contract that requires the knowledge and consent of the participating parties.