See how to detail strip and reassemble the upper assembly on a P08 Luger (also known as Pistol Parabellum). You'll take out the trigger bar spring of your weapon, 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.