De quel pays parle-t-on (kiswahili me fait penser à un système inspiré du système belge, où ces cours d'introduction et de rafraichissement des connaissances durent quelques semaines) et dans quel pays anglophone le texte sera-t-il lu ?
Peut-être est-ce first year of undergraduate studies, ou refreshing course.
First year of undergraduate studies is fine. I don't think the higher education systems of North America and the UK break undergraduate studies out in the same way as in France, so this is a description, not an equivalent suggestion for the certificate that « propé » represented back in the times when that (now defunct) course of studies existed.
"Refreshing course" (did you mean "refresher", OLN?) would not really work here. That suggests to me a course a professional takes to get updated on his special field.
PS: The term propédeutique is also used in Swiss and French-speaking Belgian universities as well as by the Catholic Church, but in each case with a different meaning. See here. It will be important to know the specific context of the term before trying to find an equivalent description in English of the intended French meaning.