It's not really a question of time or intelligence; the key factors are how similar it is to a language you already know and how much effort you choose to put into learning it while living there.What is an acceptable time period to become fluent in the local language of the nation you move to? Is 2 years the longest it should take if your not an eejit?
For instance, it's extremely difficult for Westerners to build up a large vocabulary of written Japanese (Kanji).
I'm not an expert, but Romanian (the language you're thinking of, I believe) should be one of the easiest Eastern European languages for a native English speaker to learn because it's a descendant of Latin.
It's similar to Italian/Spanish/French but a bit harder.