Why does my iPhone change correct words when typing

I need to know how to disable the iPhone from changing correct words to incorrect words. Yes I have predictive typing turned off. I want it to spellcheck words that are incorrectly spelled and don’t make sense, however I do not want it to change ANY of my correct words to gibberish. This is a plague for the iPhone.

It doesn’t matter if I reset the keyboard or attempt to train it to stop changing my words. I wanted to completely stop changing correct words

JUST spell checking only for NOT words