power steering,Problem with steering on one side only.

I bought this car from a person, and few days later I noticed a strange behavior of the steering. When I turn the steering wheel max to the left, it does not come back to center. The steering wheel stays in that position and the car turns with jerks. However, if I turn the steering wheel to the right then everything is normal and the it goes back to the center.
Moreover, the steering does not seems to to be very stable on bumps. I feel like the steering wheel becomes slightly free-moving. While normally, the steering should continue in stable non-free-moving way even on bumps.
In addition, the