Video: Getting Started with Ionic & Firebase

Hi, sara
very helpful getting started video but I was just wondering how if someone creates a ecommerce app with ionic and firebase as backend part then suppose product list is rendered from firebase url and then once user is authenticated how to make sure whatever user adds to cart stays there in the cart for that particular authenticated user so even if the users closes the app he/she can still see the items that he added previously in his/her cart once he logins again if logged out...? and one more thing like once user adds item to cart it needs to be stored on different url other than used for product list url as previously said and one last thing once i authenticate user with google auth and i go back to the browser to see that firebase url i dont see user data there even if user login shows why?
Thanks really would be helpful if you would answer this..