loosing power going uphill then catches and recovers(knocking sound startup only

Knocking is most likely piston slap, as these certain GM engines were known too have. Sounds as though car was not maintained very well.

Catches do you mean detent in transmission.

Have a mechanic take it on a test drive!

Good Luck! I started out like u many yrs ago. 96 lumina very good engine will go 400,000 if u take care of it ..oil changes etc. That's common, knocking on start up. Check your tranny fluid, if that's ok it could be many things but I'm guessing your tranny may be going. I've got 212,000 & still have great engine & body but it has been so many things throughout the years. Intake & timing chain cover gaskets ...not cheap! I use only str8 gas,no ethanol becuz ethanol eats the gaskets. If it starts to nickel & dime you decide early if u want to keep it or not. I have over 15 g in mine in about 14 yrs but no car payments for 13 yrs. Overall 1 of the best engines Chevy ever made.