Why does my Ouma look confused when I use 'nie' at the end of the sentence?

I’m a heritage learner trying to reconnect with my SA heritage, but I keep accidentally doubling up the 'nie' everywhere. My family speaks a very colloquial, fast-paced version of Afrikaans, and I feel like my textbook 'double negative' is making me sound like a robot. How do I drop the second 'nie' or soften it to sound more natural, or is there a specific rule for when it’s actually required in casual conversation?