I think you should consider delete your Shopify account and cancel your Shopify subscription. Here's our guide on how to do it the right way
I'm Miles from the Social Care team at Shopify.
There are a couple of ways you can completely start again. As suggested above, you can look at closing your account and creating a new one. This is a great, fast option for you. The one thing you'd need to keep in mind is your current .myshopify.com domain would not be able to be used again. If that's not a problem, you're good to close the store. To close your store, simply login to your admin and go to Settings > Plan and Permissions. Under "Store Status" and click "Sell or close store" and follow the steps on the screen. Check out our help doc for more information on pausing and closing stores.
If the domain is important, then you'll just need to delete everything you've worked on so far. The best advice I can give is to go through each menu item on the left-hand side and deleting everything. I've summarised below the things you'll need to look at deleting:
If you get stuck at any point, please let me know so I can help out.
I'm interested to know why you're wanting to start again. Was there anything you've been struggling with or need assistance for? If so, please don't hesitate to let me know.
We have a great program called Shopify Compass which I would highly recommend. It's full of free courses around store design, marketing and more. You can also sign up for live webinars.