Complex sentence: From 2004-2005, Cellars worked in the German Foreign Ministry as a Transatlantic Exchange Diploma with a follow-on assignment as the Management Officer at the U.S. Embassy in Berlin, where he was the Embassy liaison officer to the White House during the G8 Summit.
Split into simpler sentences: From 2004-2005, Cellars worked in the German Foreign Ministry as a Transatlantic Exchange Diploma, and had a follow-on assignment as the Management Officer at the U.S. Embassy in Berlin. In the U.S. Embassy in Berlin he was the Embassy liaison officer to the White House during the G8 Summit.