You can simply continue the windows installation in Chinese and make sure make a microsoft account and login and actually look for updates and complete the whole installation process. I just did it on my new 2017 12.5 ” Mi book Air 8GB RAM 256 SSD version.
It’s working great in English now, says Windows is activated with a digital license linked to your Microsoft account.
No need to purchase any shady keys from Ebay or any of that shit 😀
Here’s a how to I used:
http://en.miui.com/thread-585720-1-1.html