As someone who writes short stories for fun, I don't recommend using too much dialogue unless it either forms a focal point of your story/you know how to make it natural. Dialogue is used to reveal things about the conversing parties + their relationship with one another, but I feel this would work mostly in a much longer text than what you'd write in an exam
When I do imaginatives for school, I mostly avoid dialogue by just having one character (or sometimes, when I have two, I tend to use minimal dialogue towards the end to reveal something groundbreaking/leave on a cliffhanger). If you're not confident with writing dialogue, it would be best to do without it.
