Complex sentence: As soon as he started to go to school he realised that sharks weren't just a passion but also a goal and since 6 years old he said to everybody he was going to study the great white shark.
Split into simpler sentences: As soon as he started to go to school he realised that sharks were more than a passion, they were a goal. Since 6 years old he said to everybody he was going to study the great white shark.