The past simple in English is easy but it has some specific issues that need a lot of practice like irregular verbs, try the following exercises on the following websites:
1. from Agendaweb, where you have lots and lots or work to do from simple affirmative sentences to intermediate level.
2. from My English pages
3. from Ego4u
Well done!
PRACTICE OF THE PAST SIMPLE
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Anterior
GRAMMAR AND VOCABULARY REVISION FOR LEVEL 1
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