Stalling, Sputtering, shutting off

I bought a 2011 Chevy Malibu at the end of
February 2022. The check engine light has been
on since 2 weeks after I got the car for cylinder
one.  I’ve gotten fuel injectors, spark plugs,
harness, fuel rail, solenoid sensor, grommet rail,
mass air flow sensor, & air filter replaced. And
now my car will sputter and get stuck at 10mph.
I’m now being told I need a new engine, but the
mechanic doesn’t know for sure. He’s been
playing a guessing game since he started
working on the car. I’ve had other people tell me
it’s my transmission, or throttle position sensor.
I’m not really sure what to do at this point and I
don’t want to spend money getting things fixed
that do not need to be fixed.