See how to detail strip and reassemble the lower assembly on a P08 Luger (also known as Pistol Parabellum). You'll see how to remove the takedown lever of your weapon, and remove and install the trigger and more.
Be sure to follow all disassembly and assembly instruction found in the technical section of http://www.lugerforum.com.
If you are not sure of what you are doing or if the gun is not working properly, take it to a competent gunsmith.
Be sure to follow all NRA firearms safety recommendations.