New Seller Urgent Advice

Started this store three days ago with a cool little product and now I have over $500 in sales. Nice but there’s three main problems. One, the inventory I sent to Amazon FBA has still not been shipped. I had to switch from Fufilled by Amazon to Fufilled by Merchant in order to keep the listing active which I’m not sure was a good idea or not. Three, I clearly have no idea what I’m doing and I urgently need advice on how to proceed or what I should do. Maybe pause the orders for awhile?