It's not that he can't speak English, it's that the English that he knows is all mechanical jargon. Like, he can't tell you what he had for lunch yesterday, but he's aces when it comes to gaskets and pistons. My dad knows all the nouns relating to refrigeration and automobile engines. He doesn't, however, grasp the purpose of verbs that don't screw, weld, grind, or cut. And the most important adjectives are either quick or slow (sometimes broken). In English he can order parts for an air conditioner over the phone, but the mechanics of a sentence are beyond his reach.
And like a family of cogs set in motion, he repeats: on the phone we compare the weather in Miami to the weather in New York, then we discuss corrupt government officials, then we tie it all together by ranting about climate change. Each and every conversation we have has this structure. But no two are exactly the same. In the world of efficient and precise machinery, then, we're broken and inconsistent. I wouldn't trade it fer nothin'.