“the presence.” The Hebrew text is more literally, “from in front of,” but in the Hebrew culture that expression would be taken idiomatically to mean “from his presence,” and not literally “from in front” of the person as if you could just move to his side and be fine.
“will not understand.” The Hebrew is in the perfect tense, and thus more literally, “have not understood,” but the sense of the verse is future. So, it seems the verse is saying that a person who has no understanding will not gain knowledge by staying around foolish people. The Bible makes it clear in many places that who we choose to spend our time with affects how we think and act (1 Cor. 15:33).