How to fix MacBook Air screen half page

Hi,

I'm not sure "screen half page" you mentioned, though if it can't display half page of your MacBook Air screen, it could be back light or LCD issue. Try to check your display with Apple Diagnostics if it reports LCD related error.

Use Apple Diagnostics to test your Mac - Apple Support

If it doesn't help or error reported, you'd better take your MacBook Air to your local retail AppleStore, Genius Bar or Apple Authorized Service Provider to be examined your MacBook Air there.

Genius Bar Reservation and Apple Support Options - Apple

Find Locations - Apple

Service and Repair Providers for Apple Products - Official Apple Support