Complex sentence: Following his graduation from the "Langemarck-Realgymnasium"--a secondary school built on the mid-level "Realschule" to achieve the "Abitur" (university entry qualification)--in Singen he volunteered for military service in "Luftwaffe" on 1 November 1937.
Split into simpler sentences: Following his graduation from the "Langemarck-Realgymnasium"--a secondary school built on the mid-level "Realschule" to achieve the "Abitur" (university entry qualification)--in Singen. He volunteered for military service in "Luftwaffe" on 1 November 1937.