L'impératif: Comment dit-on en français

Comment dit-on en français?
Let's work! !
Do your homework! (pl.) vos devoirs!
Don't speak English in class! (pl.) => anglais en classe!
Be nice! (pl.) => gentilles!
Be nice! (sing.) => gentille!
Let's go to the movies! => au cinéma!
Study! (sing.) => !
Go to the library! (sing.) => à la bibliothèque!
Let's dance! => !
Don't lose! (sing.) => !
Let's finish! => !
Don't buy this dress! (sing.) => cette robe!
Let's not have a dog. => de chien.
Let's go! => !
Speak louder! (sing.) => plus fort!