You need to use Mi home Xiaomi version 5 and higher (Play Store).
Yes you require Mainland China locale for all of your components 100% available. They have 'other' but unfortunately in our case sensors based on Zigbee Gateway Xiaomi not found in manual list.
You could try Europe or other servers but you'll get offline issues with devices.
If you are worried about security I suggest you compare Mi Home to Facebook or Messenger even MS Windows 10 agreement!
If you want English translation (98%) set your language to this. DO not leave on Android default setting in this Mi Home app!
Mi Home is a ECO Centric Smart Monolithic control app for all PARTICIPATING manufacturers distributing through Xiaomi China. There are alternatives such as Home Assistant.
You require the Gateway hardware as well by Xiaomi - Zigbee standard to talk to those sensors.
And much more important: Xiaomi China just announced freeing up of all their APIs of their smart products to the world.They are involved in a 65 billion dollar expansion float according to the "Australian Finanical Review" There presence into the US is going to be strengthened.
The translations into English are continuing at an unstoppable pace.