JSFin I see literally no comment that will help you! xd
Building an online store is pretty hard for a beginner as you need to know both front-end and back-end.
You also need PHP you handle the transactions, refound, etc. Stuff that I don't know off. And it might be even more complicated than just that. A PHP developer can help you better with this.
Here is a tutorial that builds the front end for a store.
But you can always build a store using wix or wardpress.