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]])
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. AT: "all he wants to do is argue" or "he craves arguments" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here the word "They" refers to anyone who teaches anything that does not agree with the teaching of Jesus. The phrase "have lost the truth" represents ignoring it or forgetting it. AT: "They have ignored the truth" or "They have forgotten the truth" (See: [[rc://en/ta/man/translate/figs-metaphor]])