Автор спутал все случаи употребления Present Perfect и Simple Past в этом упражнении....

Question

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 didnt go to the theatre this month. 3. Did you have holiday this year?— Not yet. 4. What are your plans for summer? — I didnt think about it yet. 5. Weve discussed some of these problems last time. 6. When have you bought this car? — Two years ago.

Answer 1

1. She has read (read) a lot of books last year. (сигнальное слово last year – Past Simple)
2.We didnt go (haven't gone) to the theatre this month. (сигнальное слово this month – Present Perfect)
3. Did you have (Have you had) holiday this year?— Not yet. (сигнальное слово this year – Present Perfect)
4. What are your plans for summer? — I didnt think (haven't thought) about it yet. (сигнальное слово not yet – Present Perfect)
5. We've discussed (discussed) some of these problems last time. (сигнальное слово last – Past Simple)
6. When have you bought (did you buy) this car? — Two years ago. (с вопросом When? – всегда Past Smple)

Answer 2

1. She read a lot of books last year. - Past Simple потому что last 
2. We haven't go to the theatre this month.- Present Perfect потому что this month 
3. Have you had holiday this year?— Not yet. - Present Perfect потому что yet
4. What are your plans for summer? — I haven't think about it yet. - Present Perfect потому что yet
5. We discussed some of these problems last time. - Past Simple потому что last
6. When did you buy this car? — Two years ago. - Past Simple потому что when