Buying financed cars – does anyone have a glimpse?

Hello, would like to buy me a car financed by a private seller. The car is not financed by the manufacturer’s house bank, but there is a branch of this bank in my city. So far, but the constellation in my case is not quite understandable: A financing is after all a loan contract consisting of lender (=bank) and borrower (=in my case the seller)?! ->Here is a problem for me that the contract The bank is the owner of the car, since it is not yet fully paid. The current seller would become the owner with payment of the last installment, right?! Would it be possible for the seller to request the letter from/at a bank branch near us? There the letter could then be triggered and the vehicle could be transferred to me as a buyer. Is that true? Ask me only if it is a problem, if the holder is not present or maybe knows nothing about the sale of the car? What rights does the registered holder have in this case? How does this affect me as a buyer? Does someone know about it? Would I be very happy about an answer!