correct, format and convert a simple Java project to Spring

A simple JAVA project will be provided. The project is a beginner's quiz game app. The code is not properly formatted therefore it needs to be improved (all entities have been included in the user but need to be separated, the game is limited but can have added functions, a programmer will know what to do), there are some functionalities missing and the relational database needs to be changed from mySQL to PostgreSQL.
Java Persistence API has to be used and tables with CRUD API need to be created - the focus is on the structure of the Service and Repository layers. The application must have a part where business logic is encountered. CRUD APIs for entities should be exposed and the Get API should allow filtering by fields that make sense and sorting by at least one field and pagination. At least one API should make a call to an external service and display the response. Swagger is to be configured and APIs to be documented.
The project should additionally be accompanied by proper documentation with explanations of functionalities (such that someone inexperienced can read about it and understand what has been done).