Car trouble..... How can I sell my car

I know this isn't related but... Idk where else to ask right now. Maybe someone knows..

Husband and I bought a used car that he financed. He's paying like 200 something a month for it. Anyways, turns out this car has an oil leak which we have to fix.

When we found out we took it to a shop that was supposed to fix it which I thought they did but months later aka now I'm still having this leak. So wonder if they even fixed it.

Is there any sort of way we can sell this car or trade it in or something to get a different car? Thanks