My texting app is missing. I need to reinstall it I guess

The message app cannot be deleted. Try restarting your phone OR look for it in the App Library. You can also search for it in Spotlight. When on the home screen, try dragging down and search for the app.

You cannot delete Messages

Go to App Library which is after your last home screen.

Tap and hold on the Messages icon til it jiggles then drag in back into a home screen