Make a pull request

I would like to make a pull request to add a feature to the users-permissions plugin.
Update the current user, like PUT to /users/me
Do I need to fork all the strapi project? (Its my first time doing this)

You can’t fork a single file. If you are using github website to edit a strapi or any project file it automatically forks the project for you, then you should rename it to remember what that fork was intended for, make the neccesary changes then open the PR. Github will guide you all along. For vscode you can install github pull requests extension to help you, and the process is basically the same.