Hey Potato, Git thinks there’s another repo inside this one, so it is trying to add this as a submodule instead of just saving your changes to the README. This usually happens if the guestbook repo is inside another Git repo on your computer.

Try cloning the guestbook repo into its own folder and check to make sure none of the parent directories have a .git folder. You can quickly test this in the terminal by running git status in the folder before cloning anything to see if a repo already exists.