Unfortunately, I can't recreate your issue on my end. Double right arrow only skips stuff you seen (unless you have the option that skips unseen text). Can you check whether you have that option off?
You can't delete persistent data in Android through the app itself, but you can do so by clearing the data through your phone settings.
If you click Menu while running the game and then click Menu again, you can return to the main menu at any time, but unsaved progress will be lost.