Is the five hundred Euros paid by the insurance company halal or haram, knowing that insurance is forbidden in Islam, and my commitment to it was due to the compulsion of French law, in addition to seeking honesty in the transaction?

Legally, the errant man bears the responsibility for his mistake, and the law does not change this ruling. Therefore, there is no harm in benefiting from what was given to you for your car due to his error. For whoever damages something must pay its value or its equivalent, whether intentionally or by mistake, whether an adult or not, and whether directly or indirectly.