Answer:
The correct answer is Antes, aprender nuevos idiomas me era muy fácil, pero la semana pasada traté de aprender unas frases criollas y me fue muy difícil.
Step-by-step explanation:
It is very common to confuse the perfect past with the imperfect past.
The big difference is that the perfect past is used to indicate an action that took place in the past, at a specific time and that's where it ended. On the other hand, the imperfect past is used to describe an action that happened in the past in the usual way, even if that action is over.
Let's analyze the given sentence in parts:
Antes, aprender nuevos idiomas me era muy fácil: Here it is appropriate to use the imperfect past, since it is not talking about an action that happened only once in the past, but it was usual for this person to learn languages before.
Pero la semana pasada traté de aprender unas frases criollas y me fue muy difícil: Here he is clearly naming a specific time in the past: last week. Both actions happened last week, "I tried to learn" and "it was very difficult for me."
Therefore, given this information we can say that the correct answer is Antes, aprender nuevos idiomas me era muy fácil, pero la semana pasada traté de aprender unas frases criollas y me fue muy difícil.