When I first started to learn German in Berlin, I suddenly figured out in myself that I would not be able to speak or understand this language easily and it actually turned out so. Basically German and English both belong to the same Germanic language and hold a lot in common in words and grammar. Therefore It is regarded that once you learn to speak English then why not German? But it was not so simple in my case.
I myself tried to give an analysis and explanation of my own case. First I found out the hypothesis that people who do not speak English at all learn German even better and faster than I do. To be honest, it was true to some of my Japanese friends around me.
They kept saying that German is much easier than English. Then I started to analyse the difference between them and me. Why can they learn German better and faster than I do? Is that simply because they are smarter than I? Probably yes. But the answer easily conjured up when I asked one of them how to make a past participant sentence in German. To make a past participant sentence in German, you must put the verb in the end of the sentence, which is one of the biggest grammatical differences between German and English. My friends, non English speakers, accept this rule and try to translate a sentence from Japanese to German following this rule. On the other hand, my process was a bit more complicated than theirs. I accept the rule first and compare it to English and translate it from English to German. Now the difference between them and me is clear. I needed to take one more extra step than they did in making German sentence just because my brain automatically compared it to English one. Having noticed that fact, I started to try to bear in my mind to forget all about English when I read, hear or speak German and now see how it works.
The process of learning languages contains lots of unexplainable elements and riddles Some can learn it much faster than others and some can read it but not speak it at all for some reasons or the others. In other words, so many men, so many ways. For me, this elusiveness is one of the most interesting aspects of getting touch with languages.