If you were connected via Facebook or logged into a H5G email account before you lost all of your progress, you will be able to get your progress back by simply logging back into your account. You can do this by tapping the three lines at the top right to open the side menu then tapping on 'Log Out.' You will then be given the option to sign into your H5G email account or connect via Facebook.
If you lost your progress as a Guest by logging into a Facebook or a H5G email account, you can just log out of that account by tapping the three lines at the top and tapping on 'Log Out'. When given the log in options, tap on 'Play Now' under 'Guest.' Please note, H5C does not guarantee your information will be stored when playing as a guest.
If you were playing as a Guest and you lost all of your progress by uninstalling the app, or losing your device, then it is not possible to restore your progress.