Car purchase step by step

Hello community, first of all thank you for the opportunity to ask for help here. I have unfortunately no experience with the cars yet, but hope that it will change soon. Since I cannot assess it financially, I would like to spend a maximum of €1,000. To secure myself financially: 1. Scenario. I buy the car and it turns out that several expensive repairs are necessary, insurance and fuel costs cannot be borne by me. Conclusion: the car must we g. What options do I have? What are the costs? How does it work? Which documents are necessary? 2. Scenario it is not so dramatic How does the purchase process proceed? Which documents are necessary? How is the registration, re-registration, insurance? Would be very grateful if someone would explain to me how the car purchase takes place. And prepare me for it) Thank you all!