Hello,
I have navi in dash mirror something like http://en.yftech.com/RA02-5002.html (RA02-5002) with front and back camera.
I can download only China map from application and also everything is in Chinese language. I don't know if it's possible to change firmware to have english language (if it is please help me with this) but for sure I wanna have map of europe.

Firmware version is ra02l.evb.160518
Android 4.xxx

I advise strongly against messing around with the firmware when you are not 110% sure what you are doing and especially when you have never done it before. And even then you could turn the device into a paperweight.

When you have a manual (can be a booklet or a CD/DVD) search for it. In it may be a description how to change settings by pressing which button how many times. Or contact the seller or manufacturer. On that website in the upper right corner it says "contact".