doc: Modify the README. md,DATABASE.md, and BACKEND.md files

[Aditya8369]

I would like to change these files to understand the project easily for the new contributors helping them to understand the project properly.

@Renu-code123 I would like to modify the above files

[github-actions]

Thank you for raising this issue!

We'll review it as soon as possible. We truly appreciate your contributions! ✨

Meanwhile make sure you've visited the README.md, CONTRIBUTING.md, and CODE_OF_CONDUCT.md before creating a PR for this. Also, please do NOT create a PR until this issue has been assigned to you. 😊