My very limited understanding is that some interstitial language data is used to map between languages, but they are often somewhat "polluted" by the idioms or idiosyncrasies of whichever language you first start with to build it up.
I seem to recall, for example, google translate having difficulty with the word "plane" between two non-english languages, accidentally confusing the word with two meanings from English. This was, iirc, because the internal representation of the words were originally generated by an English dataset, and so airplane in one non-english language became to level wood with a planer in the other non-english language (or something to that effect).
Mandarin / Chinese has a comparatively simpler grammar (no verb conjugation) and no phonetic alphabet with arbitrarily varying phonetic rules, it is also chock full of idioms and homophobes. There is a lot that can be done, but the 80 / 20 rule is in full effect.
I seem to recall, for example, google translate having difficulty with the word "plane" between two non-english languages, accidentally confusing the word with two meanings from English. This was, iirc, because the internal representation of the words were originally generated by an English dataset, and so airplane in one non-english language became to level wood with a planer in the other non-english language (or something to that effect).
Mandarin / Chinese has a comparatively simpler grammar (no verb conjugation) and no phonetic alphabet with arbitrarily varying phonetic rules, it is also chock full of idioms and homophobes. There is a lot that can be done, but the 80 / 20 rule is in full effect.