S6 autocorrect won't work?

[Android Central Question]

I have all the autocorrect features turned on and yet with all my typos, none of them get corrected at ALL. The only thing I can think of that would cause this is that at one point I had accidentally programmed something in incorrectly so a common username of mine kept getting autocorrected to an incorrect version of said username, so I had to delete that correction, and I think I may have had to wipe the autocorrect. If this is the case, how do I reprogram in corrections, and in the future how do I delete just the one correction so this doesn't happen again?