Macaws have the ability to learn dozens of words and short phrases in their lifetimes. What most people do not know about these wonderful animals is how they learn. Most parrots who can speak pick up both sound and pitch by listening. Which means if you say “hello” in a high-pitched voice, the bird associates the word with its tone. Next day, if you say “hello” in a deep, rumbling voice, you haven’t made any progress at all, since your macaw expects to hear “hello” in a high tone.
Stick to one word at a time in the latter days of your training. Once your macaw learns one or two words, it becomes much easier to learn more. It should take just a week (or even less) per word.