He is unqualified to be a mechanic. Not sure whether the disqualifying factors
are intelligence or truthfulness. But even if you are not a mechanic, you
probably would do better than he did and at least you would know what you did.
Whatever you do, DON'T take the car back to him!

My guess is either a problem with the clutch itself or a clutch maladjustment.
In either case it would not be too difficult or expensive to diagnose and fix.

One of the real advantages of having done the job (or helped or even watched the
job done) is that you would have realized how ridiculous his claims are.
--
George Downs, Bartlesville, Heart of the USA!