Celso,

Based on your response to User Profiles in Office 365 Simplified , I am marking this question as resolved. 

Where is the solution?

That is my question too

Attributes such as Manager, Department and Title can be looked up from the User Profile service.

To get started, the Nintex Forms application needs access to User Profiles in the Tenant.

Navigate to Site Contents and click on the Nintex Forms app.
On the next screen at the top right there is the Nintex Forms Admin menu.
Click the Allow Application Access to User Profiles link which will take you to a page to trust the app.
This action needs to be performed by a tenant administrator.

To display attributes in a Nintex Form the userProfileLookup() runtime function is used.
For Classic and Responsive Forms drag on a Calculated Value control onto the canvas and enter a formula such as : 

The function requires two parameters. The first is the users Email address (In this example I have used the "Common" reference of Current User (Email)) and the second is the attribute to be returned.
New Responsive Forms do not have a Calculated Value control but User Profile attributes can be displayed in a Text - Short control as the "Default Value".
The Default Value formula is formatted like:

Note that the Text - Short control may not populate in Preview mode when using a New Responsive Form so publish the form and test it by creating a new item in the list.