Someone gave me a car to take over payments and I’ve been paying on the car for 5 months. Now they want it back. It’s still financed in their name

Just because the former owner wants the car back does not mean that you have any obligation to give it back.  If you can prove that you have a contract to purchase the car in exchange for making the remaining payments as they come due, a court will order that you keep the car.  That being said, if you have no written contract, it may be difficult and possibly impossible for you to prove your claim, and you have to decide how much it is worth to you, in term so both money and hassle, to try to keep the car in court.