In Google’s SEO Office-Hours Hangout last December 17, John Mueller was asked about multi-language sites, if sites are better translated as a whole or if it is ok to have only specific pages translated. Would a site that does not have all pages translated be considered less comprehensive and therefore, not rank as well compared to a site that is fully translated? Is it ok for the foreign language version to link to the English content?
John’s answer is that they look at language on a per-page basis, and not as a whole site. It is not so much that they try to understand a part of the website is Spanish and a part is English, they essentially look at an individual page and say – it looks like the page is in Spanish and when someone searches for something Spanish, they will be served that version.
From that point of view, it does not matter if only a part of your website is translated in a different language as that happens normally. Usually, you start somewhere and you expand from there, when it comes to translating a site.
With regards to internal linking, it can be a bit tricky in that it could provide a bad user experience if your internal linking is all focused on the English version.
However, if you have pages which are English only and you link to them from the Spanish version, that also happens and is pretty common across a lot of websites.
For the most part, if you have the Spanish versions of your pages, then make sure that the Spanish versions are also properly interlinked but if there are individual pages that are not in Spanish, then link to the English one, at least.
So generally speaking, Google looks at a site at the page level and it is ok for a multi-language site not to translate the whole site fully, it can only be the important parts of the pages, depending on the capacity.
The important thing is that they are internally linked together. It seems like it is best practice to link similar languages though linking to the original version, should not cause much of a problem.
You can watch the full Google SEO Office-hours hangout episode here:
The particular question is at the 31:00 mark