It sounds bizarre because it's incorrect, attempting to say two contradictory things at the same time, I've studied and I'm studying. You can't say "j'ai été" followed by en train de + infinitif (it calls for participe passé or adjectif, or nom - "j'ai été étudiant pendant 2 ans", and passé composé (finished action) followed by en train de is a contradiction


You got it right down below. English past continuous tense is most often constructed in French using the present and an adverb (most often depuis). "I have been studying French for two years" is "J'étudie le français depuis deux ans", meaning you've been studying for 2 years, and you're still studying it. In very specific cases, when the action gets interrupted by another (but not necessarily ended), you could use l'imparfait" "J'étudiais le français depuis deux ans lorsque j'ai lu L'Étranger...". I had been studying French for two years when I read..." If there's no interruption, you don't use imparfait.

If you use passé composé, you mean you've stopped studying. It's not for "I have been studying" but for "I have studied French for two years". Passé composé shouldn't be used with "depuis" but with "pendant", as the action is completed : J'ai étudié le français pendant deux ans (during two years). Any way you try to construct this with passé composé will turn out ackward or incorrect (except in very specific cases, for instance if you want to say "I've studied French for two years... and I still do!".

Construction with "en train de" are used for ongoing action in the present, for "I'm studying" etc., not for "I've been studying". It can also be used with imparfait, for interrupted actions "J'étais en train d'étudier, lorsque..."/"I was studying when..."



Actually, present + adverb is the only correct solution in this case.



Right, although it is exactly the same as saying "I have been studying French for two years". Depuis juste sounds ackward to my ear (It sounds like a copy of "for only" and might be an anglicism, but I'm not 100% sure. The more French people speak English, the more of those bad constructions appear and it's hard to keep them straight). When in doubt... Seulement would work better here, "depuis seulement 2 ans, or "depuis 2 ans seulement". Using the present + depuis has all the same connotations to native speakers as "I have been... ing".