As a part time job, I teach German, here in Germany, to teenagers (the interval goes from 15 years of age to 18) who have fled their lands due to war and general political instability. The come from different backgrounds; in the class I am teaching now, I have Eritreans, Afghans and Kurds. This, in order, implies the fact that they speak different languages (Persian, Tigrinya, Kurdish and Arabic).
The main problem I am having is, apart from discipline, making them understand, as an example, what the subject of a sentence is, or what a verb is. I have reiterated many times over the standard definition of verb, that is A verb is a word which expresses an action, but they do not seem to fully comprehend what a verb is unless I list a few of them.
I am not a Deutsch (Lehramt) student; indeed, I study Mathematics. This means that I do not have the pedagogical tools to cope with this problem. Does any of you have even a remote idea of how to even slightly improve their understanding of words representing abstract ideas, that is, words whose meaning I cannot visually convey? For they need to learn what a verb or an attribute is, this is unentbehrlich for students of German of any level.