using of modal vreb "must"

[Marina]

Have i changed the following sentences correctly?
1. Water your plants right away, or they are going to die.
You must water the plants.
2. Jeck has very poor teeth because he eats so much sugar.
He must not eat sugar.
3.I will go shopping after breakfast.
I will have to go shopping.
4.I got up early to catch the 7.30 train to London.
I had to get up early.

[Alan]

Yes, all correct.