I would suggest hiring an expert. They can help uncover these potential problems allowing you to focus on business. But if you do prefer to do it yourself, I would recommend running a few usability testing sessions, these can really help uncover the core usability problems. This allowing you tweak your design to make it work better with your users.

Hey! For getting started ii not ecomm I would recommend Shopify. Easy set up and payment. They also have thousands of themes to choose from and will help with shipping options.