You need to develop your awareness of tenses. Is someone asking you about the past, present or future? Is a modal being used (can, would, should, etc)? Listen to the tenses in the questions and answer appropriately. Here are a few questions to practice with. Read the question and answer in the appropriate tense.
1. Why do people drink coffee?
2. Why have people learned to cook complicated foods?
3. What can be done to help people affected by rules that say they must retire?
4. Do you remember the first time you caught public transport on your own?
5. Why did people in the past dress differently than we do today?
6. If you had a chance, would you make a movie? Why?