Is the gift from the contractor to the supervising engineer, which he claimed to be an expression of brotherhood and not for personal gain or bribery, considered a bribe or a gift?

This gift is forbidden because it might influence the supervisor to overlook the engineer's shortcomings. This is based on the Prophet's (peace be upon him) saying: "Gifts to workers are unlawful gain," and "What is wrong with a worker whom I send out, and he says: 'This is for you, and this was given to me as a gift'? Why doesn't he sit in his father's house or his mother's house and see if he is given a gift or not?" It is not permissible to accept it unless the employer authorizes it.