How do I delete a word from auto-correct?

So I'm trying to remove this impropriate word. Not gonna show you the word because it's impropriate. I tried many tricks, I tried long pressing and it didn't do anything and I tried to clear the google keyboard's data but I have a different phone so it doesn't work. The device I'm using is a Vivo phone, the model number's 1811. Do anyone know how to remove words from the auto-correct? This is all the information I got. Update, It turns out I don't have GBoard so I downloaded it. I've been using my default keyboard the whole time. Sorry about my mistake.