Regardless of the level that you are teaching today, it’s always essential to stop mid-stream multiple times during the class and do a comprehension check. There are several ways you can do that.
My most often go-to way of doing comprehension checks is to stop just after a sentence or phrase containing a new word and ask in English: what does XYZ mean? For words that you KNOW are difficult (nothing close to a cognate, for example, or a false cognate) do this every time the word is used.
Comprehension checks. Every level. Every period. Today!