Hi maryann0301,
welcome to the Apple (user-to-user) Community!
Re: "Icons are all black along with white letters in my text"
Seems you may have accidentally inverted the text colors to white on black ?
To check: Open the Settings app,
then tap "Accessibility"
then tap "Display & Text Size".
If either "Smart Invert" or "Classic Invert" is on .... turn that off.
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Re: How to change text size on iPhone 13
To change the text size on your iPhone
First: Go to Settings
Tap "Display & Brightness".
Then: Tap "Text Size".
Finally: Drag the slider left or right to change the text size.
If needed:
Useful Resource: iPhone User Guide - Apple Support (Click the "Table of Contents at the top to see contents")
iPhone support website (info. / support / contact options etc.) : iPhone - Official Apple Support
All the best :-)