Complex sentence: Charnley was "the Seasiders"' top scorer for nine seasons., including five consecutive seasons starting in 1958--59, when he scored a total of 26 goals (20 in 35 league games and six in six games in the FA Cup).
Split into simpler sentences: Charnley was "the Seasiders"' top scorer for nine seasons. He was top scorer for five consecutive seasons starting in 1958--59, when he scored a total of 26 goals (20 in 35 league games and six in six games in the FA Cup).