Is my Luger jammed?

[Enoch]

As will shortly become painfully obvious, I know nothing about Lugers. I inherited my dad's Luger when he passed away and basically locked it in my (his old) gun cabinet and haven't touched it in years. Recently my son expressed an interest in seeing it so I hauled it out and tried to show him how one would chamber a round. The "thing" that you grab on either side and pull straight up on only slid back about an inch and then stopped. Also, the safety is in the down position and I can't slide it up. I tried inserting a magazine thinking perhaps the gun required a magazine in order to be "cocked" but that didn't have any impact. The gun, from the outside, appears to be well oiled and there's no rust or significant loss of blueing. In other words it hasn't been allowed to deteriorate and has never been misused. Can anyone help me understand either what I'm doing wrong or what may be wrong with the gun? Thanks in advance for any assistance anyone may be willing to offer.