1. Can't you do better than that?
=> Is that the best you do?
2. Why don't we go shopping this weekend?
=> Shall we go shoping this weekend?
3. I don't want to do anything too enerdetic today.
=> I don't feel enerdetic to do anything today.
4. It isn't necesarry for students to wear uniforms on Wednesdy.
=> Students don't need to wear uniforms on Wednesday.
5. She teaches English well.
=> She is a good English teacher.
@DX