What is the ruling on the money that a father takes from a contractor in exchange for supervising the unloading of trucks and covering the workers' expenses, while retaining a portion of the amount for himself as payment for his additional work? Is this money considered theft or a contract? And what is the ruling on the financial gifts that the contractor sends to the father in exchange for his service?

It is permissible for your father to deal with the contractor outside of his official working hours, provided that he has no role in the company's dealings with the contractor and is not responsible for supervising or evaluating him. He may supervise the unloading of trucks, but he is not allowed to take anything from the workers' wages except with the contractor's knowledge or after an agreement with him. As for monetary gifts from the contractor, if your father has a supervisory or evaluative role, or influence over the continuation of the contract, then these are forbidden and considered ill-gotten gains (ghulul). However, if he has no relation to the contractor's work with the company, and the gifts were in return for his supervision of unloading shipments, there is no harm in them in the future after agreeing on a clear wage, while returning the previous amounts or seeking the contractor's forgiveness for them.