Complex sentence: Between 1943 and 1944, he taught sculpture at the School of Art of Braunschweig; however, he came back to Austria because of the bombardments that his native country had undergone.
Split into simpler sentences: Between 1943 and 1944, he taught sculpture at the School of Art of Braunschweig. However, he returned to Austria because of the bombardments that his native country had undergone.