Github fork has created a project. How can it contribute some of its modifications to the source project?

  git, question

After modifying some codes, I feel that some of the modifications are universal and suitable for open source, while others are personalized and not suitable for contributing to the source. However, there is no secret and they can be stored in my own project for maintenance.
How should I operate?

If you have passed sufficient tests and feel that you can submit it back to the original project, please refer to GitHub’s official tutorial:https://help.github.com/articles/creating-a-pull-request/