RAD STUDIO XE 10.2 Create Online and Offline FMX Database

About us : we are developers with the principle of providing convenience to our customers, considering our customers who do not understand technology. how we give something in a way that is simple and easy to understand for our customers. What we're looking for : Experienced Android developers to work on database applications online and offline in real time using RAD STUDIO 10.2 We need someone to work on the database, authenticate users, including building an API or front-end service or back-end, translating our requirements into technical requirements. This is an ongoing project, so chances are we will work with you later. This project requires experience with : This project was first created using RAD STUDIO 10.2 , so you just continue it. We already have the UI design, so just build it. - We work with databases with 5 million items. - Sync data from server to client at any time and make it offline or data stored on the device (external storage). - still able to work even though it is in sync with the server. - Notification to the client every time there is a change of data on the server. - use a listview filter to search data and display the data on the listview in less than 5 seconds (listview is very slow to display large data, note: 5 million items). - Making simple user authentication. - import csv or txt to offline database. Give your best idea for what online database to use? In your proposal, feel free to share a brief summary of your experience and tell us about the new Android projects, such as what's ideal for our project.