thinking about it, with no dictionaries,google translate, possible cultural and worldly differences in their language(whose to say Mary's language is the only one in this world, and what concepts do they have that are completely foreign to humans) and so much more, sure he could learn basic nouns and verbs through repetition and such(R.I.P no anki) but the fastest way for him to understand would be for mary to fetch linguistics professors to study him and his language, theyd be a lot more equipped for this situation and could probably get him to understand even their grammar to form sentences....plus im sure linguistics professors would die for a opportunity to study a completely new language