The private data has two functions. First, it is necessary for your convenience. You can specify your contact information (e.g. phone number or Skype) in your profile and hide it from public access. When agreeing to a tour you need to give the customer your contact information, you can add it to a message by clicking just one key, without entering it manually. Second, the service administration can easily contact you if necessary.
The app works on Android and Apple.
Tourists transfer payment directly to the guide. The service is not involved in this.