Complex sentence: He began his youth career with CD La Morenica, and later joined SD Ponferradina as a cadet; however, he was dissatisfied with his time at the club and returned to his previous team at the end of the season.
Split into simpler sentences: He began his youth career with CD La Morenica, and later joined SD Ponferradina as a cadet. However, he was dissatisfied with his time at the club and returned to his previous team at the end of the season.