。
Yumi studies English hard.
Literal
Yumi [topic-は] English [object-を] with-all-one's-might study.
一生懸命 is one of Japanese's most characteristic adverbs — 'with one's whole life on the line,' literally. It intensifies effort, a word every Japanese learner meets early. The kanji are 一 (one) + 生 (life) + 懸 (stake) + 命 (life). Originally 一所懸命 ('to stake one's life on one place'), from the samurai era.