You shouldn't worry about the details. You don't need to learn the papers by heart, the only thing you do need to know is the main idea of the professor's research and the key purpose of it.
Start with the basics, try to find the definitions which will help you understand the subject and the methods professor used in the papers.
I had a similar situation when I had to work on the research paper on Linguistics (and believe me or not, I know nothing about Linguistics at all), so I had first of all to learn what my Professor was up to in her papers (as it turned out it was Mystery and suspense bullying
in the Gothic Tradition). Consequently, my paper was dedicated to the Gothic Tradition texts. So I started from defining what Gothic is and how it is connected with Mystery. Pretty easy as for my Mathematician's mind (I just created a scheme to better understand the terms).