Complex sentence: However, in April 1990, Yamaguchi decided to end the partnership to focus on her singles career, and with no one of her caliber to partner with, Galindo returned to singles competition.
Split into simpler sentences: However, in April 1990, their partnership came to an end when Yamaguchi decided to focus on her singles career. As there was no one of her caliber available, Galindo returned to singles competition.