Hi @Jamil Saif ,
Donovan is one of the best out there! I took a look at your diagram
Start with tutorial over at https://learn.microsoft.com/en-us/azure/app-service/app-service-web-tutorial-auth-aad. Even though this doc is using securing apps with Azure Active Directory, the structure of the app is a front-end with a back-end. You can add both the front-end and back-end to a vnet to retrict traffic so that the back-end only responds to traffic that's on the vnet e.g. the front-end. Want to throw in a database, check out this tutorial and make sure you secure it. Reverse proxy documentation is here, albeit I don't see a need a for it as your diagram shows it isn't connected to anything.
Hope you find this help.