Suggest me something

I'm looking for a solution to my fb marketplace.
What I need is When I post something on fb marketplace & a potential buyer send message something like "Is this product still available?"
I want an auto reply to this message.
How to do this auto reply?
What apps or software can do this?

I checked on manychats but only seeing fb messenger but i'm not looking for messanger auto reply or chatbot.

I want something for FB Marketplace.

It's for personal FB marketplace posting
I just need to reply one message when someone enquire "Is this product still available?" or anything similar. Will get a preset auto reply.