Change the language of application according to the default language of quest device.

I'm developing an application in VR where I want to display content in 2 languages in English and in Arabic. What would be the standard of developing such application. 

1) I can put up a toggle button on each panel where I'm showing some description to convert text to English or Arabic.

2) I can get the default language of device if its Arabic then I can only show the text in Arabic and vice versa.

How to know the default Language of device if I have to opt second option?