NHTSA Complaint #11417738 — 2017 NISSAN PATHFINDER

My 2017 Pathfinder started with a grinding feeling and noise while driving , then it would start but would not go in drive or reverse, with 51,000 miles. I had it towed to the dealership where I purchased it new , with all types of warranty as an additional cost to me ...on inspection they said a code P0776 pressure solenoid B from low CVT fluid from a leak at the drain plug , they replaced and found no other leaks, they also replaced all stuff that was not a problem including wiper blades, did not change oil but replaced air filter, and element and a few other things to fill his cache my cost for all of no problem solved was $ 734.70 . I was back with the same problem and an additional plume of blackish grey smoke on starting up with an awful smell. my car was not fixed on 2nd encounter I took my keys after waiting for 3 hours because for their new diagnosis i would again have to pay out of pocket in spite of all such warranties which covers none of the presenting issues. i am back again for the 3rd time .. their diagnosis is " the engine is gone and is beyond them fixing it, I can only drive the car until it dies with no guarantee when ..can some please assist I am a 71 yr old woman and , still owe $ 22000. 0n this car. Nissan advisers or corporate somebody please help.