ODPOWIEDZ! - Français

J'ai eu --> action qui a eu lieu une fois, ou action brève.

J'avais --> action (ou situation) qui a duré dans le temps ou était habituelle, qui est désormais terminée.

Exemple : J'avais 20 ans quand j'ai eu ma première voiture.

Exemple : J'ai eu un accident de voiture quand j'avais mon appartement à Paris.

It is complicated indeed. French speakers have the same problem in the other way!

It's all about the duration : you can imagine the past time as a long line. On this line, sometimes events happen ; or you do some actions ; you hear something ; etc.

On the line :

- let's say there is always a "general context" : you were someone / you had some occupation / you went around with someone... somewhere in the past (for instance : two years ago and for some period) : that was the general context of your life then -> IMPARFAIT (j'avais)

- but there also appear some specific and momentary events on the line. Some which will be marked as crosses or so... For instance : you won a contest (at a specific date) ; you succeedeed in your exams (a specific year) ; you had an accident ; you met someone (specific time and place...) -> PASSÉ COMPOSÉ (j'ai eu)

* * En 2013, je n'avais encore que deux enfants. J'ai eu mon troisième enfant en 2014. (Mon troisième enfant est né en 2014.) J'ai trois enfants.

** En 2012, j'étais étudiante. J'ai obtenu mon diplôme au mois de juin 2012.

Here you can make the comparison present perfect / passé composé but be careful.. because it's rare!! I mean that you can say :

"J'ai étudié l'histoire." (this applies that this experience belongs to the being you are right now... quite like present perfect so)

But this sentence is also correct : "J'étudiais l'histoire [cette année-là]"... (you just talk about you past occupation... as a past one)

Attention : all of this is the same when you talk about a very close past. It should be no problem if you keep in mind the same image of a regular line where specific events appear...

-> Hier, j'étais au restaurant quand tu m'as téléphoné.

Ce matin, j'étais encore au lit quand le facteur a sonné.

It's never about the length between the event and now ; always about the nature of the activity ---or sometimes about what we want to tell about it (do I want to say that I used to study something some years ago ; or that I have studied something and then I know things about it now...)---.

Il y a une heure, j'étais au travail.

Il y a une heure, je me suis endormi au travail.

-> "Il y a une heure" doesn't matter itself.

**** I hope this will help!! ****