Using the past tense instead of the past perfect
The train already left before I arrived.
The train had already left before I arrived.
Don’t use the present tense and the past perfect in the same sentence. It would be incorrect to Say: My brother says that he had not gone to the cinema last night. Use the past perfect when the time of one past action is more past than that of another. Put the action which was completed first in the past perfect and the second action in the past tense.