 Complete the following phrase:  On 14 January 1940 Rökker was transferred to the Luft-Nachschub-Kompanie 5 5th Aerial Replacement Company stationed in Gütersloh. From 4 July 1940, he was stationed at Berlin-Gatow with the Schülerkompanie Flugzeugführer-schule School Company at Advanced Flying School. Rökker was promoted to Gefreiter on 1 October 1940. He then completed advanced training at a flying school near Magdeburg from 20 March15 August 1941. Rökker attended Blindflugschule 5 in Belgrade, 