You can always click on any completed skill if you want to practice it again. But if you want to restart a tree or remove the language completely, you'll need to follow these steps:
- Go to your settings page.
- Go to your "Language" page by selecting Learning Language from the menu on the right of the screen.
- Click Reset or remove languages under the big blue "See all language courses" button.
- Select "Reset Progress" (blue button) if you want to start the tree from the beginning. Select "Remove" (that's the big red button) if you want to remove the tree and any traces of it, such as the small flag next to your name or on your profile—but this last option will only be available if there is more than one course on that list.
Please be aware that removing or resetting a course cannot be undone.
If you remove a language, you can always add it back later, but all your progress will be lost and you'll have to start the tree from the beginning.