1. Go to Settings
2. Select “Biometrics and security.”
3. Tap on “Secure Folder"
4. “Lock type.” Choose between Pattern, PIN, Password or a biometric option like fingerprint or iris, and create that password.
1. Accessing Secure Folder where a duplicate of Google Tasks was created requires password but,
2. The Google Tasks outside Secure Folder can be accessed anytime.
I think there should be a Samsung built-in app encryption or app lock.
Thank you, alleacj, for sharing your comments and inquiry, here.
You can download S-Secure (Secure Folder) apps at the Galaxy Store to have this feature and use it to lock your individual apps/folders on your Samsung Galaxy A51.
Secure Folder leverages the defense-grade Samsung Knox security platform to create a private, encrypted space on your Samsung Galaxy phone. Apps and data moved to Secure Folder are sandboxed on the device and gain an additional layer of security and privacy.
For more assistance, you may contact us on our online Samsung support channels below.