Complex sentence: In June 1944, he was serving with I./JG 54, based in Courland on the Eastern front, he became Gruppenkommandeur of I./JG 54 but in September 1944 he was wounded again, this time after an encounter with a bomber.
Split into simpler sentences: In June 1944, he was serving with I./JG 54, based in Courland on the Eastern front. He became Gruppenkommandeur of I./JG 54 but in September 1944 he was wounded again, this time after an encounter with a bomber.