Автор спутал все случаи употребления Present Perfect и Simple Past в этом упражнении. Помогите найти ошибки и объясните их.

1. She has read a lot of books last year. 2. We didn't go to the theatre this month. 3. Did you have holiday this year?— Not yet. 4. What are your plans for summer? — I didn't think about it yet. 5. We've discussed some of these problems last time. 6. When have you bought this car? — Two years ago.