Applying for Hilfsassistenz for Ersti courses

I am a first year masters students in maths who enjoy teaching quite a lot and hence I am keen to be a Hilfsassistenz. I am conversational in German and can read without much problem, but not fluent enough to be conducting a class in it. Is it possible to be a Hilfsassistenz for the Basisjahr courses (analysis, linear algebra) which are conducted in German, speaking English?

I've heard of some international doctoral students doing it for some engineering mathematics courses, but how does this work language-wise? Concepts are introduced in lecture in German and then the students have to relearn the names in English when they come to exercise classes?