Email support@mobileregatta.com. Include the device model and what you were doing when it went wrong. Reports of chat or racing conduct can also be made in the app: long-press a lobby message, or a name on the results screen, and choose Report. Every report is reviewed by a person within 24 hours.
In the app, Settings has Delete my online data, which removes your profile, rating, chat and reports, and takes you off the leaderboard. The privacy policy says what is kept and for how long.