In 13:15 God describes the people of Israel as if they have physical diseases that cause them to be unable to learn, to see, and to hear. God wants them to come to him so he will heal them. This is all a metaphor describing the people's spiritual condition. It means the people are stubborn and refuse to receive and understand God's truth. If they would, then they would repent and God would forgive them and welcome them back as his people. If the meaning is clear, keep the metaphor in your translation. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "heart" refers to the mind. Alternate translation: "these people's minds are slow to learn" or "these people can no longer learn" (See: [[rc://en/ta/man/translate/figs-metonymy]])
They are not physically deaf. Here "hard of hearing" means they refuse to listen and learn God's truth. Alternate translation: "they refuse to use their ears to listen" (See: [[rc://en/ta/man/translate/figs-metonymy]])
They have not literally closed their eyes. This means they refuse to understand. Alternate translation: "they refuse to use their eyes to see" (See: [[rc://en/ta/man/translate/figs-metonymy]])
"have me heal them." This means God would heal them spiritually by forgiving their sins and receiving them again as his people. Alternate translation: "have me receive them again" (See: [[rc://en/ta/man/translate/figs-metaphor]])