You can help correcting, improving and extending this documentation by clicking on the "edit" button on top right of each page that brings you directly to the corresponding file in the documentation repository on Github. You can edit the page using the rather simple markdown language. Then you commit your changes by choosing a meaningful commit meassage and the "Create a new branch for this commit and start a pull request" option. After internal review and discussion (if necessery) we will merge your pull request into the documentation repository and then it will be also visible on the website.
If you want to create new pages, have a look at the README file of the documentation repository. There you will also find a description of how this website is rendered and how inserting a new page into the navigation works.