Deleting the account removes for good your nickname, cards, coins, dust, progress, achievements, ranking place and your player number from the first players' rewards. Matches played against you stay in your opponents' history, but without your nickname. Backups lose the data within 30 days at the latest.
Write to faunaarena@gmail.com with the subject "Delete account" and your nickname. If the account was linked to Google, write from that Google address. If the account has a password, the easiest way is to log in with it in the game on any phone and delete it yourself. For an account without a password or Google, also give your player number, title or roughly when you created it, so we don't delete someone else's account. We will delete the account within 30 days, confirm by e-mail and remove your address from the tester list if it was there.
More about your data: privacy policy.