To disable activity sharing
1. Open the Bigin app on your iPhone.
2. Tap the
More 
icon at the bottom right of the screen.
3. Select
Settings 
.
Under "Manage Privacy", you can find the title "Privacy & Security".
4. Tap on Privacy & Security > Share Activities with Siri.
5. Tap the
toggle switch
to disable activity sharing with Siri.

Note: Once you've disabled activity sharing, your Bigin app usage pattern will stop being shared with Apple.