Dear Adele,
thanks for your answer.
I know about exporting the gradebook.
However, concerning the assignement, this download of feedback files (pdf of quiz, or of checked written test) does not work (Moodle 3.3) when there are no submitted assignements by students. What works is upload of feedback files only, but I need download.
In the setting I am using teacher uploads feedback files into assignement, together with registering the grades for each student.
PS: See also thread here.