Don't have to, don't need to and needn't

1. My father doesn't have to work in winter because he has a seasonal job.

2. I don't have to be in that german course but I think It's very interesting.

3. The car park is free. You don't have to pay to park your car there.

4. You didn't need to take a taxi. You could have taken your car.

5. I understand you perfectly. You needn't explain further.

6. Alex has enough food at home, so we needn't go shopping today.