1. Before they came to visit my grandparents, I had already cleaned the house. (Correct tense - Past Perfect for action completed before another past action)
2. After Jimmy had gone home, I was doing the shopping. (Correct tense order)
3. She had come to the cinema before I did. (Past Perfect for completed action before another past action, "did" instead of "do" for past tense)
4. When they arrived, John went away. (Simple Past for action completed at a specific time)
5. I had prepared for the exam and was ready to do well. (Correct verb tense - Past Perfect for preparation, Past Continuous for ongoing state)
6. She had eaten dinner before she went to the movie. (Past Participle of "eat" is "eaten")
7. By the time we arrived, the concert had already started. (Past Perfect for action completed before another past action)
8. He realized his mistake when he had left the keys at home. (Corrected tense order - realization happened after leaving the keys)
9. They had visited Paris many times, but they had never seen the Eiffel Tower. (Both verbs in Past Perfect for completed actions before an unspecified point in the past)
10. After he had finished his work, he went for a walk in the park. (Corrected tense order - walk happened after finishing work)
11. She had gone to the store and bought groceries for the week. (Past Perfect for going to the store, Simple Past for the action of buying)
12. By the time the guests arrived, I had already cooked the dinner. (Past Perfect for completed action before arrival, past participle for "cook")
13. Before she moved to New York, she had lived in Chicago for five years. (Past Perfect for living in Chicago before moving)
14. When we arrived at the hotel, our room was already cleaned. (Passive voice - room was in a cleaned state)
15. He lost his keys, so he couldn't open the door. (Simple Past for losing the keys, could not for past inability)

1. Before they came to visit my grandparents, I had already cleaned the house.

2. After Jimmy had gone home, I was doing the shopping.

3. She had come to the cinema before I did.

4. When they arrive, John goes away.

5. I have prepared for the exam and am ready to do well.

6. She had eaten dinner before she went to the movie.

7. By the time we arrived, the concert already started.

8. He had left the keys at home when he realized his mistake.

9. They had visited Paris many times but never seen the Eiffel Tower.

10. After he had finished his work, he was going for a walk in the park.

11. She had gone to the store and bought groceries for the week.

12. By the time the guests arrived, I had already cooked the dinner.

13. Before she moved to New York, she lived in Chicago for five years.

14. When we arrived at the hotel, our room is already cleaned.

15. He loses his keys, so he couldn't open the door.