How to use / creat rest api for spring?

Please,
Someone could share a project, like create rest- engine, this link https://docs.camunda.org/manual/7.8/user-guide/spring-boot-integration/rest-api/ is confusing, or share project in github

you mean like the official camunda examples?

Thank you for your help.

I am studying on site camunda.org, but you have something more direct, like a document in pdf, but for development from beginning to end.