Configuration for each user

Hello everyone, I’m having difficulty with the login screen of my application, I’m using firebase authentication, and I would like each user to have their personal configuration after logging in, for example, if the user chooses to buy a product, a button would be visible , for those who don’t buy the button to be invisible, I’ve been looking for a week in the topics and I couldn’t find it, I tried several ways but I didn’t find the solution. Follow my blocks for anyone who can give me guidance.