You have as long for your answer as the court rules provide. If the governing rule is UTCR 5.030, that would appear to be 14 days from the date of service.I make no promise that is the correct rule; it's the most obvious reference to answering a motion that I saw, and there may be another rule that applies.

If you fail to answer on time, or fail to appear and defend, the court will presumably decide the motion based on the evidence and testimony presented by your ex. You should retain a lawyer.