selling on Facebook group

I am not sure if this is the right spot for this or not, but here goes....I run a group with 1700 plus members, on which I sell products that arrive at intervals. presently I have people pm me with their orders which ends up unbelievably hectic and nuts. my poor laptop freaked out last week with the rapidity of the messages coming in,
No my question is this, is it possible to set up a shop or selling system whereby I can have a simple counter? where I could enter say ten black dogs and people click on one to purchase and it automatically counts down?
I have asked a computer guy to look at it, but he's proven to be totally unreliable..

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