Refactor the backend codebase by following the Object oriented design pattern

**Describe the enhancement you'd like**
As of now, the codebase does not follow any design pattern, so it's pretty hard to make it maintainable and flexible

**Describe approaches if you have thought of any**
Refactor the backend codebase by following the Object-oriented design pattern like Singleton classes, factory classes etc

**Additional context**
**Working on it.**
