Here are the completed sentences:

1. His car can run **faster** than my car.
2. The workers in my factory work **more carelessly** than those in your factory.
3. The people in my town are **happily** living with their lives while only 38% in her city are as happy.
4. My mother can cook **better** than I can.
5. Living in the city **is more convenient than** living in the countryside.