TurboWallet uses Apple and Google single-sign-on which means it's security depends on how well you secure your Apple or Google account.
Tips for better securiting your Apple or Google account:
Ensure you have a strong password
Do not use your Google or Apple password on any other site, app or service. Make sure it's unique.
Enable two-factor authentication (2fa)
How to enable two-factor authentication
Google 2fa
Google has a dedicated 2fa page that explains what it is and helps you get setup at https://www.google.com/landing/2step/
Apple 2fa
Login to the Apple ID website. Go to Security -> Two-Factor Authentication and set it up.