So you led me down to thje right answer -> the difference is that I wanted to get the variables not from the main scene, but they were instanciated in the main scene

***code here
#In the third script unrelated to the others:

if area.is_in_group("person"):

var Person_ID = area.get_parent().get_instance_id()

var Person = instance_from_id(Person_ID)

var name = Person.Name # I needed the 'instance id' to make it work***