I have to ask about "zajęcia" and in what contexts it can be used relative to "kurs?"
zajęcia is more less "classes, lessons" in this context, ussually in higher education or outside education, lessons are lekcje in school.
kurs is a set of classes, with a goal. like a Kurs nauki jazdy (driving learning course) is aimed to teach you to pass a driving licence exam.
zajęcia is also any activities.
In relation to this sentence, a teacher can use I invite you for my lessons and for my course interchangeably, if you have to attend classes to finish course , and to take course to go to the classes.