Here the writer begins his third warning. He warns these believers that they are still not mature and encourages them to learn God's word so they can understand right from wrong.
Even though the author uses the plural pronoun "we," he is most likely referring only to himself. Alternate translation: "I have much to say" (See: [[rc://en/ta/man/translate/figs-pronouns]])
The ability to understand and obey is spoken of as if it were the ability to listen. And the ability to listen is spoken of as if it were a metal tool that becomes dull with use. Alternate translation: "you have trouble understanding it" (See: [[rc://en/ta/man/translate/figs-metaphor]])