Complex sentence: She returned to Germany in 1912 to Nernst's lab for a short stay and then again in 1915, where she was caught up by World War I and she had to stay there until 1919.
Split into simpler sentences: She returned to Germany in 1912 to Nernst's lab for a short stay and then again in 1915. Caught up by World War I, and she had to stay there until 1919.