wrote it yesterday
Lunch is more expensive than dinner= 점심식사 저녁식사보다 더 비싸요.
I have to study hard= 저는 열심히 공부해야 해요.
'딱딱하다' means something is physically hard. (e.g. stone)
If you want to say to do something diligently, you can use the word '열심히'
We have a driving lesson today= 오늘 우리는 운전 수업이 있어요.

lesson is 수업 in Korean
We had cooking practice yesterday= 어제 우리는 요리 연습을 했어요.

We like studying abroad= 우리는 유학하는 것이 좋아요.

Hope it was helpful!