Here "he" refers to anyone in general that teaches what is not correct. To make this clear, you can translate "he" as "they" as in the UDB. (See: [[rc://en/ta/man/translate/figs-genericnoun]])
# understands nothing
"understands nothing about God's truth"
# He has an unhealthy interest in controversies and arguments
Paul speaks of people who feel compelled to engage in useless arguments as if they were ill. Such people greatly desire to argue, and they do not really want to find a way to agree. Alternate translation: "All he wants to do is argue" or "He craves arguments" (See: [[rc://en/ta/man/translate/figs-metaphor]])