when did he start working with the series?
2005
Paul Lieberstein
On June 12, 2008, "Variety" magazine reported that he would become one of the executive producers of "The Office".

Lieberstein worked in the writer's room from the start of the US adaptation and was asked by Greg Daniels to act as well, as Greg wanted some of the writers to know what it was like on the other side of the camera. Lieberstein has said he "attended 'The Office' acting school" and was often thrown by Steve Carell's improv during scenes.

what is "gossip"? It is the sixth season premiere of the American comedy television series "The Office", and the 101st overall episode of the series. when did this series begin? March 24, 2005 what is the theme of the sixth season? It depicts the everyday lives of office employees in the Scranton, Pennsylvania, branch of the fictional Dunder Mifflin Paper Company. In the episode, Michael spreads a rumor about Stanley having an affair, then spreads a series of false rumors to try to convince everyone the original rumor was not true. who is the producer of this season? Paul Lieberstein where is he from? Westport, Connecticut, USA what did he start his career as? An auditor at Peat Marwick International
wiki:15874026
Paul Lieberstein [SEP] "The Office"
On June 12, 2008, "Variety" magazine reported that he would become one of the executive producers of "The Office". Lieberstein worked in the writer's room from the start of the US adaptation and was asked by Greg Daniels to act as well, as Greg wanted some of the writers to know what it was like on the other side of the camera. Lieberstein has said he "attended 'The Office' acting school" and was often thrown by Steve Carell's improv during scenes. On March 22, 2012, it was announced that Lieberstein would step down from his showrunner role to focus on a planned spin-off series featuring Rainn Wilson as Dwight Schrute, which was tentatively called "The Farm" and Lieberstein was set to be the showrunner.