why does the low oil pressure light comes on when turning left or right

First check the oil level when the engine is off. If it's low, the oil will run away from the pickup screen when you turn and the pump will suck up air. Air compresses and won't allow the pump to build pressure.

If the level is good, have a mechanic install a mechanical pressure gauge. If it also reads low, suspect worn engine bearings. You might overcome that for a while by using a thicker viscosity oil. If the actual pressure is okay, suspect the sending unit. When turning, the engine slows down slightly from the strain of running the power steering pump. That small speed reduction will cause a slight drop in oil pressure which could trigger a defective oil pressure sending unit.