how can i close my account?
Are you sure you want to close your account? It sounds like maybe it would be better to reset your progress in your language course. Just go to your settings, go to the "learning language" section, and click on the link labelled "Reset or remove languages".
...or are you trying to add a new language? You can do this by holding the mouse over the language flag at the top of the page, and selecting "Add a new course".