How do you disassemble a Deutsche Ortgies 765 mm pistol or where can you find parts?

I have a gun at home that I think might be what you guys are looking for. If you look on the left side of the handgun there is a knob that sticks out in the back of the pistol. 1.) you pull back the slide [as if kocking the gun] 2.) hold the slide back and press in the knob in the back of the gun. 3.) pull upwards while doing steps 1 and 2 and the slide should come off. TO TAKE OFF THE BARREL 1.) turn it to either the left or the right only one way works but i forget which way it is. from then on YOU ARE ON YOUR OWN