confusion on importing modules

[Gribouillis]

ModuleNotFoundError: No module named 'Browser'

As explained in the tutorial that you linked above, Python will find a package only if it is on the module search path. Concretely you can achieve this by adding the path to the parent directory of the Browser directory to the module search path. You could follow the reply that I made in this thread

Later you'll learn how to write pip-installable packages and install them in editable mode.