Is the gift given by the contractor to the supervising engineer considered permissible or impermissible, knowing that the work is carried out officially and there are no violations?

Contractors' gifts to the supervising engineer are considered embezzlement and bribery because they are given to curry favor with the engineer at the expense of work quality. An employee receives their salary for their work from their employer, not from others. Therefore, the engineer must return the private car and request the work vehicle.