I want to use FXM on the external Non-Sitecore website for tracking the click event which will download documents.
In the external website, User will login so Website is having additional details name, email, phone number etc for the user.So using FXM, can I get Name, email, phone number from the external website to the Sitecore contacts, Once I have this details in Sitecore can I trigger some goals and write some custom code to send this data to Salesforce (an API call)?
Not sure whether this is the right approach but I am just throwing it out. I can directly call the Salesforce API from the external website but I want to take advantage of Sitecore features so that I track the website analytics data.
You can trigger a Sitecore Goal on the txternal site in FXM on the button for the form.
For Salesforce integration have you considered Salesforce connect? https://dev.sitecore.net/Downloads/Salesforce_Connect.aspx