Resign as a private seller from selling to a dealer?

Hello forum, I am interested in the following: I have offered a car at Autoscout. A dealer in a far distance wanted him because he has a customer for it. So he sent me a contract as PDF with his signature. I have printed, signed, scanned and sent it back. Amount is also as agreed in the purchase contract. So now I have a much better offer from a buyer. Is the contract binding for me? What can the dealer do if I have the m say he doesn’t get the car after all? He didn’t make a deposit, because everything went by e-mail. Please not moral accusations, but only facts, or experiences. Thank you. Lapsy