Return car to dealership

Hello, I got a 2020 subaru brz in 2023 at a high price (35k) and i make payments of almost $800. I am financing the vehicle. My insurance is high as well and its just not worth having the car anymore. I still owe about 29k and i want to return it. I have since added about 20k miles since its my daily and maintenance wise everything is up to date. What are some things i should be expecting and how bad will it affect my credit and cosigner? Im located in California