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.

1 She READ a lot of books last year. Past Simple сигнальное слово last year
2 We HAVEN'T GONE to the theater this month. Present Perfect ( this month )
3 HAVE you HAD holiday this year? Not yet. Present Perfect ( this year)
4 What are your plans for summer? I HAVEN'T THOUGHT about it yet. Present Perfect ( yet)
5 We DISCUSSED some of these problems last time. Past Simple ( last )
6 When DID you BUY this car? Two years ago. Past Simple