PyCharm CE 2018.2.3 doe not recognizes project content root

I have PyCharm Community Edition 2018.2.3 and the following package structure:

folder1
    |
    |-> Package1
            |
            |-> __init__.py
            |-> Package2
                    |
                    |-> class1.py
folder2
    |
    |-> Package1
            |
            |-> __init__.py
            |-> Package3
                    |
                    |-> class2.py
            
folder3
    |
    |-> Package1
            |
            |-> __init__.py
            |-> Package4
                    |
                    |-> class3.py
                    |-> class4.py

I have to add that the packages (Package2, Package3 and Package4) are added to Package1 in runtime.
So, Package1 is one big package distributed into several folders.
All the __init__.py are empty, except for the one that imports all the other packages into this one.

When I use python I can do the following without problems:

import Package1.Package2.class1
from Package1.Package3 import class2
from Package1 import Package4

I have added, as the project content root, the following folders:

folder1\Package1
folder2\Package1
folder3\Package1

But, when I open the file with the previous imports, PyCharm cannot find the packages and classes from the last 2 folders (folder2 and folder3).
If I put any of those, as content root, first; then the others are not recognized by PyCharm and thus, it cannot find the declarations inside them.

Is there a way to achieve that PyCharm recognizes the packages and classes from all the folders, so Package1 is a big package?