Can someone help PLEASE?

Your mechanic is right. The engine would make a lot of noise if the oil pump failed. Most likely not the oil pump.

You could try heavier oil. That's what most people do when they find they have low or no oil pressure. If however your engine is just plain worn beyond tolerences, then that is most likely a temporary fix at best.

To rule out a bad guage or sending unit, hook a mechanical oil pressure guage up to it to see for sure what kind of pressure you are in fact getting, then go from there. Let us know.