Is the person whom I entrusted with buying a car required to compensate me for the loss I incurred due to his lie about the original owner of the car, knowing that the authorization was verbal?

What this person did by telling you that the car belonged to the company's manager, while the truth was otherwise, counts as lying and betrayal.

As for the issue of guarantee (or compensation), it is based on whether there is a difference in the car's price depending on whether it belonged to a manager or another employee. If its market price varies for this reason, then it appears that the one who deceived and misled you guarantees this difference. It is not necessarily the difference between the price you bought the car for and the price you sold it for. If the agent violates the agreement and causes harm to his client as a result, he guarantees the damage.