Conversion purchase contract due to permanent defects ?

Have a question to the (Laien) lawyers among you: My A2 has been in the workshop for a total of 27 days since I bought it not quite 2 years ago with X-different problems. Since yesterday, it seems that some hydraulic oil is losing and he has to be a friend again. I am tired of this scrap and I want to get rid of the box reasonably cost-neutral. Does anyone know what conditions must be met to change the purchase contract? painting business is possible after the second unsuccessful improvement attempt, isn’t it? What does it look like with cars? Thank you. Greetings from the “From Audi Hard Disappointed” world improver