i think I must study English hard .영어공부를 열심히 해야합니다

Plus, it gives a nuance about following meaning. I think I must study English hard. (But I am not sudying/cannot study it.) (나/너/우리는) 영어공부를 좀 해야하는데...(못/안하고 있다.)

i think I must study English hard .영어공부를 열심히 해야합니다.