Used car purchase: handover is not & very difficult contacting

Hello, we bought a used car after two visits and test driving, but now the handover of the car (and money transfer) has been there for over a month and now we (neither car nor legal specialists) are at a loss what we can still do, because we definitely want the car.The process was the following: 25.11.2017 Purchase agreement signed by buyer and seller, but neither the money nor the car changed the owner. h minor repairs take place (gummis, a type plate at the door, small part at the gear lever…), time inaccurate, seller suspects “beginning next week”, buyer says he has it not so hasty, more important is to him that everything is “gone” repaired. 29.11.2017 SMS from buyer to seller with several questions, seller answers a few days later to a question. It follows over the next 2.5 weeks within a distance of approx. 2 to 3 days various requests for the whereabouts of the car pe 20.12.: Buyer calls seller, again no feedback. 21.12. K reaches V. V. thinks that only one work has to be done (shift lever) and can imagine a handover before Christmas. On the same day V brings the papers of the car (letter, note, TÜV, invoices) by K at home and says that he will definitely report on 22.12. to make out more. 22.12. K assures the car and No more signs of life of V, despite various contact attempts, we telephoned through the city or the county to locate the person – we were informed that the person is generally unreliable. On 03.01.2018. V calls K to propose a handover for Friday, 5.12.. Car is only ready for the mechanic and until Friday. Handover between 9 and 13 o’clock, as V afterwards must leave. V wants to call briefly on 04.01. for an exact time. 04. 01.2018: V does not sign up. K calls V, V says he calls back because he forgot to contact the mechanic. Nevertheless, no feedback from V. WhatsApp message from K to V three hours later: “Hello Mr. XY, what did the mechanic say?” Answer: “With clean Monday noon”. Over the entire weeks several contact paths were searched (signal, WhatsApp, SMS, call). The seller said on 3.1. that he was there on vacation. We raise very strong doubts as to whether Monday to What we would like to know now:How does the seller make himself vulnerable (punishable)? How can we get the car as quickly and as peacefully as possible? How and to what extent can we claim damages? (reason: car is insured for free, I have to lend myself permanently mobile kit)