There is no account
Hifza has no accounts and keeps nothing online. Profiles, progress, marks, bookmarks and settings are stored only on your phone, so only you can delete them.
How to delete everything
In the app: More › Settings › Delete all my data. Everything is erased at once and cannot be undone.
If you exported a backup file, it is yours: delete it wherever you saved it.
Questions
Email support@sssolve.com.
See also the privacy policy.