For the Apple iPhone X series with Face ID, there are some new elements to familiarise with for authenticating apps. This quick guide will show you how to review Face ID app authentication.

How to Review Face ID Authentication for Specific Apps

Open Settings > Face ID & Passcode. You’ll need to enter your passcode to continue.
Under Face ID & Passcode, tap on Other Apps. This will bring up all apps that you’ve allowed or denied access to for Face ID.
From here, you can turn Face ID authentication on or off on a per-app basis.

If you disable Face ID for a specific app it will require you to enter the password for that particular app.

While Face ID is convenient, one may want to disable this feature for certain apps such as banking apps, as they might want you to enter your password manually.

Source: https://9to5mac.com/2018/05/02/how-to-face-id-specific-apps/