Hi @Luca_Lattarini ,
To track traffic from third party site, you can use one of the following:
* Traffic Sources reports - Referrers, Referring Domain report.
* Marketing Channel reports.
* Tracking Code report.
In case you are using specific campaigns in a link on any third party site/app, that can be passed to Campaign variable and leveraged either in the Tracking Code report or in the Processing Rules of the Marketing Channels.
Hope this helps!
Thanks!