Eunice here from Shopify, thanks for posting, and welcome to the Community!
Firstly congratulations on finishing your store, that's a huge achievement! Be sure to check out the Shopify Store Launch Checklist if you're thinking of launching soon. It's easy to miss a simple but critical step in a successful business launch so it's a super handy resource to have on hand!
With regards to design time, this is only available to you if you're using any of the 9 free Shopify themes and are on the Basic plan or higher. A total of 60 minutes of design time is available to you for making small changes and basic theme customizations. It's good to note that there are many customizations that aren't supported with design time which are listed on Shopify's Design Policy. Now you've learned a little more about design time and you think it's something that you'd like to use then you can do so by contacting Shopify Support via chat, email, or callback through The Shopify Help Center.
If you'd like some feedback on your store please drop your URL and I'd be happy to take a look. Be sure to include your store password if you still have the password protection turned on. What is it about your store that you feel is unprofessional?