OK, so, if I got that right, your problem is:
— need to use QR-Code to log into online banking
— cannot scan QR-Code, because
— the QR-Code is too blurry for me to scan, because
— I scan it from too close up to be successful
if that’s right, possible solutions would be to either
— use a smaller focal length camera/lens (which we’ve already tried)
— have a bigger distance to the QR-Code, so it isn’t so blurry anymore and meets with the fitting focus distance. Which we could try, as the QR-Code does not have to fit a specific area on the screen to be scanned (at least in the regular camera application), also you can still zoom in when a little farther away, still keeping the focus on point.
another thing which may help is using the built-in QR-Code-Scanner from your iPhone, available via search (swipe down from Home Screen), called code scanner, where you also can ensure good lighting conditions using your iPhones flashlight. Please report back any misunderstandings, mistakes, or if you were successful.