Complex sentence: He was an athletic phenomenon, as he competed in decathlon, football, basketball and volleyball.After his graduation from the Robert College in Istanbul, he moved to Athens in 1917 and ever since then he joined the family of Panathinaikos.
Split into simpler sentences: He was an athletic phenomenon, as he competed in decathlon, football, basketball and volleyball. He moved to Athens in 1917 and ever since then he joined the family of Panathinaikos.