Hi Heeeeee,
welcome to the Apple (user-to-user) Community!
Re: How do I turn off the blue box without turning off switch control?
Wondering if the "blue box" is quite empty with blue lines around it, or if the whole box is blue (turn off zoom?).
Also wondering which iOS version is installed on your iPhone, and whether updating the iOS may help:
Seems iPhone 8 can not be updated beyond iOS 16, yet there are sometimes updates for iOS 16 available.
(NB: It is wise to back up your iPhone data before updating the iOS version if needed.)
You can check for updates in Setting > General > Software Updates:
Eg: About iOS 16 Updates - Apple Support says iOS 16.7.10 is the latest (compatible) update.
or
If you haven't already: you might try re-starting your iPhone (deletes temporary files, re-establishes connections, may update recent setting changes, and often restores order if something is not working as expected.
_____________
Else, if needed:
If VoiceOver is also in use, try turning that off: Settings > Accessibility. Scroll down to turn VoiceOver off.
or
If Zoom in also in use, try turning that off: ie: Look in Settings > Accessibility > Zoom
All the best :-)