Complex sentence: His contributions were important as United retained the league title and also reached the semi-final of the Champions League after a 4--0 victory over Porto in the quarter-final, in which May scored the first goal.
Split into simpler sentences: His contributions were important as United retained the league title. The team also reached the semi-final of the Champions League after a 4--0 victory over Porto in the quarter-final, in which May scored the first goal.