Just want to give my 5 cents to perfect this ability, the idea is display 2 options for user seleccion:

First botton should be "Do you adjust to your browser language?", the second botton should be "Select which language do you want"...

This will very nice customer experience because sometimes people living in another country due local reason need to set up phone language that they can't afford to use, in this case users will be able to select the language that they afford to use.