Redmine

It is a code snippet that you can add to redmine website and then after you add this, redmine will have a google translate.
It will automatically translate the whole website depending on what language you select on the drop down menu.
Please watch the video in the link below for more information.

https://www.youtube.com/watch?v=Ey9gyrhiZWo

Thanks.

Where is official documentation?

Sorry. It is my first time to ask for feature and I don't know what official documentation you where asking.
Can you please elaborate what documentation you are asking for?
I think the link below would help.

https://support.google.com/translate/?hl=en#topic=7011755

Where is official documentation which describe steps of https://www.youtube.com/watch?v=Ey9gyrhiZWo ?