The language barrier was the hardest part of my move to the States. My memories of the difficulties with the English language are somewhat amusing today, but at the time it didn't seem so.
The first few months were the hardest. I was able to understand only about 60% of what people were saying. Everybody was very nice about it, but it was very hard on me and my ego. In Italian I loved to play with words, discuss the various meanings and interpretations of various ways of saying things and I loved to dig deep into the details of the Italian language.
All in a sudden I felt very “slow” and somewhat lost.
In general I could express what I wanted, but I couldn’t get most of what was told to me. Do you know how frustrating that is? You ask something, you get a 5 minutes answer but you understand only 3 minutes of it. You hope that the other 2 minutes weren't very important. At the end you look lost hoping that there is more, but there isn't. Usually the worse is that the 5 minutes speech included a final question that got lost in translation. The person is now staring at you waiting for an answer or some kind of sign but you have no idea what the question was, or if there was a question at all.
There are a few uncomfortable seconds where the person you are talking to realizes that you are lost, and his expression goes from a smile to something different. You start looking thoughtful to take time and you end up asking “can please you say that again?”. The second time you get the short version of the answer, which doesn’t usually contain what you really needed to know.
After a year or so, things started to slowly switch in the other direction. All in a sudden I reached the point where I could understand 90% to 95% of what people were saying, and I developed the ability of making up for the lost 5%-10% with reasonable accuracy; but now I found myself not able to talk in the way I was able to understand. I couldn’t express the complex thoughts and concepts that I wanted to express. I had to simplify everything (hard for somebody that loves to discuss details like me). This phase wasn't as frustrating as not understanding others, but sometimes it can be somewhat embarrassing.
You are there trying to find the right word or expression and you know from the listener's faces that you are not making any sense. Even when you can say it, you can’t quiet get the correct and exact meaning that is in your head.
Another “danger” in this phase is that you try to translate directly from your original language words that you don't know. This works some of the times, but some of the times what you say is simply not English (I still do this at times).
The worse is when what you say happens to be English, but its meaning is completely different than what you meant!
I'll give you an example. In Italian "corn" is called "mais", pronounced "mice". This word doesn’t sound Italian, so it is one of these words that I would try to use without translating, hoping it was understandable for the listener. Now imagine being in a restaurant and asking for a mice salad.
Another hard thing to do is mastering these sets of words that in English sound the same and to an untrained hear ARE the exact same. A classic example is “bear”, “beer”, “bird” and “beard”. Gosh! It took me forever to be able to say the right word at the right time. You end up saying things that sound like “I’ll have one more bird and then I need to go shave my bear because it’s getting late; I really want to be done in time to watch that documentary on beards and beers on the Discovery Channel.”. Oh well.
Another twist on these difficulties is when you know the word in English, but you pronounce it in a way that ends up sounding like something not appropriate for the circumstances, or maybe even offensive. A horrible word for that is “sheet”. My mouth wasn't able to say it without sounding like something else (not exactly white). I was aware of it so I was always trying to avoid having to talk about sheets. The same thing for the word “beach”. I would simply try to avoid speaking that word in public with fear of offending somebody. Eventually you get used to the fact that people here can hear your accent and they know exactly what you are trying to say. Nobody really cares about these mistakes.