Here is a link: http://devdocs.io/
I can't believe I forgot that.
For example I'm not able to disable any of the enabled APIs.
Are you sure? Did you try clicking the "Select Documentation" button at the bottom? I'm pretty sure you can disable those...
Also by selecting one of the APIs the URL changes but by refreshing the page-content gets changed.
I don't see any page content changing, what do you mean?