We can't currently translate that part: Topic subscriptions - receive a notification whenever someone posts a new comment in a discussion you are interested in.
Topic on Talk:Talk pages project/Feature summary
@The RedBurn: Thanks for noting it! I’ve now prepared it for translation. A translation administrator still needs to approve the edit until it becomes actually translatable, but hopefully that will happen within a few hours. (When it happens, it’ll appear on your watchlist if you watch the page.)