Aww, that's amazing! One of my mum friends' son is the same age and she says it's such a magical phase kasi parang overnight nalang sila get it na, di ba? The fact na he's not just memorizing but actually using the words ay super impressive, that means he really understands, hindi lang repeat-repeat lang. You must be doing something right with how you're talking to him and explaining things. Enjoy this phase because it goes so fast!