I don't do tags in foreign languages on my English page, but I do translate my videos into all possible languages available via the YT interface. 55% of our views are from international, I want to make sure the algorithm has all it needs to serve the videos up in those 90+ countries, should someone search there for matching tags.
I highly recommend you translate.
Here's advice straight from the horse's mouth:
"Additionally, you can offer translated titles and metadata for your videos, which may help surface them when people who speak other languages search for those keywords. Offering localized titles and metadata can improve the discoverability of your videos in search results and what’s suggested to viewers across the platform, especially when coupled with translated subtitles."
from: creatoracademy.youtube.com/creatoracademy/page/lesson/captions#yt-creators-strategies-3
The 'what’s suggested' is a potential gold mine of views if you can place on suggested on a popular video in a foreign market with low competition, since you translated your meta-data, but your competitors did not.