Why does my M/WA noun class agreement feel so robotic when talking to my Kenyan relatives?

I grew up hearing Swahili at home, but I usually just resort to basic sentences because I'm terrified of messing up the concords. Every time I try to use a slightly more complex sentence involving the M/WA class, my aunt chuckles and corrects me. How can I stop overthinking the agreement markers mid-sentence and actually sound natural instead of like a textbook?