Let it refill and repeat the pump down. Don't fill it with a water truck.

The well just isn't producing much compared to its volume. Might be ok, but it's a hint to think about the future.

Was water running in from the surface? Is the well house nice and tight? Rodent proof ?E coli almost always gets into wells from the surface, and there's nothing for it to eat down there. Frankly it's an indicator that poop got in the well somewhat recently (not years ago).