Hi Menguti,
Welcome to the Apple Community.
We are all Apple users, like yourself, and would like to help.
Wondering, which iOS version is installed on your iPad Air.
and
If restarting hasn't worked, whether you tried to "force restart" your iPad Air ?
NB: Scroll to "Force Restart" in thus Apple article
Restart iPad – Apple Support
Apple Support has another article online:
If your screen is black or has frozen
Follow the steps for your device.
If your iPad won't turn on or is frozen – Apple Support
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If the above hasn't worked, and you still need help:
You might want to check out this Apple Community discussion thread, and follow the guidance there.
iPad Air has black screen and force resta… - Apple Community
More discussion threads:
:
Black Screen on IPad Air. - Apple Community
Black screen Apple iPad Pro 11 inch - Apple Community
Seems Apple does want its customers to be happy with the products they purchase.
May be worthwhile giving them the opportunity to evaluate your iPad Air.
See a list of Apple phone numbers around the world.
Contact Apple for support and service - Apple Support
All the best :-)