Complex sentence: He was 13 years old when he felt compelled to become a good swimmer after his father drowned in the Danube River, and then took the name Hajós (sailor in Hungarian) for his athletic career because it was a Hungarian name.
Split into simpler sentences: He was 13 years old when he felt compelled to become a good swimmer after his father drowned in the Danube River. He took the name Hajós (sailor in Hungarian) for his athletic career because it was a Hungarian name.