Running a retail business is tough when you first start out. What you're experiencing is pretty normal.
Use the retail interactions as much as possible. One after another. Really nag them! This will make their interest bar increase faster. Then, it's all about gaining Perk Points you can use in the Retail Perks panel. The first one I save up for is the faster checkouts (don't get the re-stocking just yet. At this stage it's better to close the store, restock, then open the store again. But checking out those customers is really slow at the beginning and you want to get through that process as fast as possible so you don't miss other sales because he customers will give up easily in the early stages of your store.
Then, save up for either Curious Shopper - which will make the customer stay longer in your shop before they give up and walk out, or Serious Shopper - customers will enter your shop with a higher interest to purchase items.
Make sure you have enough stock available before you open your store and then get all your family involved with using those retail interactions. Every time they use one and the customer responds well to it, you earn a perk points. Those perk points are what will eventually make your store more fun to play, but it's a hard repetitive slog at the beginning- just like in real life!
Also to make more money, when you run out of produce, close your store and remove the restock signs. Then bake more goods and replace them. This is cheaper then restocking. Continue to do this until you have the Cheaper Restocking perk.
Once you have all the important perks - fastest checkout, instant restocking, serious shopper etc, you won't have to close your store to restock, you can start dividing your family into different tasks, such as baking, sales, restocking and your shop will run smoothly and make lots of simoleans.
Also, when running a bakery, try to grow a Garden at the same time. Grow the fruits and veggies that are used in your products, and once you get those harvestables to a PERFECT state, the price of your produce goes sky high!
Also, as your cooking and baking skill increases you'll be able to offer more expensive items and increase your profit margin by increasing the price mark up. (Another reason to replace your produce instead of restocking, until you're offering all the high ticket items, then change to restocking). Don't be too tempted to increase the mark up too early, it will only be harder to make sales. Keep it at about 25% for a while until your family has earned a few perks, then increase it. Eventually you'll be able to completely rip off your customers and they'll come back for more.
Once your household is making decent earnings, you can think about employing other sims. There are perks for that too.
There is a bit of strategy in the retail system and my suggestions are of course, just one way to go.
Hope you have fun with your bakery. (of course, if all the hard work doesn't sound like much fun, there's always cheats for those perks ...)
