Пажалуста помогите сделать 2 и 3

2.
1) Can you swim well?
You can't swimm well
2) Is he allowed to come?
He is not allowed to come
3) Must he come at 6?
He must not come at 6

3.
1. The airplane should fly at 3 o'clock yesterday
2. We must to help our friends
3. He could dancing well in his youth
4. May we come in early?