I don't have enough money, so I don't buy sea food.
⇒ If I had enough money, I would buy seafood.(Câu điều kiện loại 2: If+ S1+V2/V_ed,S2+ would/could/might + V_inf)
My younger sister usually spends four hours a day to practice speaking English.
to practice--> practising
Sửa lại: My younger sister usually spends four hours a day practising speaking English.
Cấu trúc với spend: S + spend + time/money + V-ing.