What answer can I give someone who asked “Do you ever imagine what our life would look like together in the future?” This person in question, you barely know him and the chances of you two being together is kinda impossible and you do not really like him

You could respond with something light and non-committal, like: "That's an interesting question! I think everyone imagines different possibilities for the future, but I prefer to focus on the present for now. What about you?" This way, you acknowledge their question without getting into specifics, and it keeps the conversation going without making any commitments.