Hi @Roxana_ElenaUrdea sorry for the late reply but I think what you need are the group and item classes in the arcgis.gis module.
When you create a project in the Business Analyst web application, a group is created behind the scenes. All project layers and output from analysis are then stored as items in the portal and shared with that group. Your question seems to be about accessing items, is that correct? If so you can use the content method of the group class to retrieve the list of items shared with a group. From there you can manage individual items using a variety of methods from the item class.
I hope this is helpful- please let us know if you have any follow up questions.
