GitHub explains you can fork, modify, commit, push and trigger a pull request. They also explain that you can still modify, commit, push and the request is updated on the website.
I would like to know if it is possible to do the exact same thing but not being the author of the fork? I am the owner of a repo with pull requests I would like to correct myself but still discuss afterwards... I was trying to push my changes into the author's repo (thinking some right access would be calculated) but the access is denied.