Update PRIVACY.md

Proposal: Expand and complete Red's privacy policy

PRIVACY.md

@@ -1,3 +1,19 @@
 # Privacy Policy
 
-The app has nothing to store, but settings.
+#### The application uses the permissions provided by the user only for purposes of proper functioning
+
+* The application does not store any user data, device usage data or call forwarding data.
+
+* The application does not transmit any data to any external source.
+
+* The application stores only a small amount of data related to the application parameters, which are necessary for the proper functioning of the application, these data do not leave the device.
+
+## Third party service
+
+* The application uses third party services for call forwarding, these have their own privacy policies, please read them at:
+
+Signal: https://signal.org/legal/#privacy-policy
+
+Telegram: https://telegram.org/privacy
+
+Threema: https://threema.ch/privacy_policy/