Hi together, the following situation between buyer and seller within the family. Private car purchase, which is recorded in writing in the purchase contract, with a standard form from the Internet. (Mobile/ADAC/etc.) The whole was agreed in instalments, which were all paid so far, monthly. There is not a single delay in payment. 1/3 of the purchase sum has been paid with the rate. The remaining 2/3 are still outstanding and continue according to the contract with the rate. gbrief was with the buyer, because of registration etc. was forgotten to give the seller back into his care. Is of course not good and cuddly, but because of lack of time and new job. Now there was a dispute and seller demands the vehicle letter because he was guided to remember for the second time. (Understandable) There was a 2 day period and the buyer reacted because he did not want to stress any more by transferring the remaining full purchase amount (The 2/3 still open The next installment would only be due in the following month. The seller now claims to want to sell the car, because by paying the complete remaining purchase sum (2/3), which he wants to remit again to the buyer the contract would be void. Because indeed on instalments was agreed. Of a special payment or closing rate nothing is in the form. The contract itself states “The vehicle remains the property of the seller until the full payment of the purchase price.” He wants to keep the car and is dependent on it, had various costs already (repairs, insurances, maintenance etc.). Is the contract invalid/invalid because the “rate payment” was broken by complete transfer? Can the seller sell the car, although there was no payment delay as soon as he has the vehicle letter again? And that is what the contract would be void of? Can the buyer insist on the instalment payment as soon as he has his 2/3 Retrieve?