Your organization will need to have dynamic surveys enabled to use this feature. Click here for more information.
This will allow respondents to change their response language while responding, in case they misclicked a wrong language at the beginning of the survey or the survey was sent as email invites and a wrong language had been set during the sending process.
1. Open a survey and go to Build-view, click "Settings".
2. On the General-tab you can set the language selection for the survey via dropdown "Show survey language selection". You have the option of only showing the language selection before the survey as well as showing it before survey and allowing respondents to change their language while they are giving their response.