If you don’t answer a message in a timely manner, the other person has to assume either you haven’t received it or you chose not to respond. If they believe you haven’t received it, their only recourse is to message you again. If they believe you chose not to respond, they might have some feels about it.
It’s always better to respond quickly even if you can’t fully answer the contents of the message. If you can’t answer quickly, acknowledge the receipt and come back to it later. Acknowledging helps the other person know that the ball is in your court and you will get less follow-on pings.
Assuming you actually do come back with a response later, it will help build trust since you followed through on what you said you would do.