Updating Shopify Inventory - No previous experience with postman

What I would like to build is something where I can upload a spread sheet to a URL (ideally I would automate this probably separately from this program).

Once spread sheet is uploaded to the URL Postman gets a list of my inventory, updates the quantities based on the uploaded spreadsheet the pushes the adjustments back to shopify.

Bonus: The spread sheet is coming from an FTP server which is password protected. It would be a bonus if I could have it set to automatically pull updated spread sheet from the server directly and action the update.

Really what I want to know at this point if this is possible. Would be happy to receive tips of how to accomplish this but I more then happy to do the research work if its possible.