3. How to change the language back to English in X1 2nd gen?
For the X1/X1 2nd gen/X3/X3 2nd gen/X3MKIII/X5/X5 2nd gen:
1. Turn on your DAP.
2. In the Main menu, scroll the wheel(or press the 'Next' button) until the cursor is moved to the gear icon which means 'System setting' (at the far right in X1/X5/X3 2nd gen/X5 2nd gen/X1 2nd gen/X3MKIII or the bottom right corner in X3), then press OK buttom.
3. Scroll the wheel or press the 'Next' button until you see the language option(it will appear in English as 'Language/****' ), then press OK.
4. Select the language you prefer and press OK.
For the M3:
Check this instruction of how to change the language on M3: click here.
For the X7 (latest firmware), X5 3rd gen, or X7MKII: