Thanks for reaching out to the Apple Support Communities. I understand you've had some trouble with predictive text on your iPhone, and I have some information that may help.
You should be able to disable predictive text using the information in the article below.
How to use Auto-Correction and predictive text on your iPhone, iPad, or iPod touch - Apple Support
If you run into any trouble, or if the symptoms persist, please reach out again.Best Regards.