How to use my iPhone as a screen for my Mac

Depending on the extent of the Damage to the screen, it is possible there are other issues with some other Internal Components of this machine.

Should that be true, getting an External Display which is a very good idea, could prove fruitless. Hopefully Not though 🤞

1 - Have the computer evaluated by the Professionals who have the Special Hardware Software and Expertise to diagnose the issue and offer possible solutions

2 - Make an Appointment at the Apple Genius Bar and have them evaluate the computer

Not an iPhone, as far as I know. It’s possible to use an iPad as a display for a mac, but even that is problematic since you’d have to initiate this from your mac.

An easier solution is to get an inexpensive external display and attach it to your mac. The mac detects the display automatically. Note that you will need the appropriate cable and perhaps an adapter, depending on the mac model and the connections your display provides.