Is it permissible to take the compensation amount that exceeds the cost of car repair and donate it on behalf of the giver, after he has waived it and refused to take it back?

The compensation amount for an accident includes car repairs and compensation for its depreciation in value. If money remains after that, the original ruling is to return it to the one who caused the accident. However, if the one who caused the accident waives their right to it, and you knew that the car was not yours, then the excess is a permissible gift. But if they waived it based on their assumption that you own the car, then the excess is rightfully the property of the owning company, because the payer intended to appease the true owner.