These exercises will help you to study English by following book:

Raymond Murphy
Essential Grammar In Use with Answers
A Self-study Reference and Practice Book for Elementary Students of English

Present and past

1. am / is / are
2. am / is / are (questions)
3. I am doing (present continuous)
4. are you doing? (present continuous questions)
5. I have done (present perfect) and I did (past)
6. is done / was done (passive 1)
7. If we go ... / If you see ... / etc.