Crafty Product and sales manager.

I started learning precast and sales ranging when I made my Shopify store. I had 1 employee who handled all my orders and I did the rest. I viewed my inventory daily and ordered what I needed at night, then I viewed my sales and made up the total revenue for the day and profit and and typed it on a separate document in google so I would have all the information if I ever needed it. I received a request from one of my clients if I could be a temporary product and sales manager fr half a year as he was starting his own company and wanted some advice of how to get started.