To answer your 'question' part, my mom never went to school but can speak passable English. She is one of the many examples I've personally seen of people who can't read or write a word of English, but can speak enough English that they are understood. To answer your 'details' part. Yes, it depends on the accent though. I myself find it extremely difficult to understand the British and Australian accents, but never had a problem with American accents, unless the person speaking happens to be someone from down South. Cheers.

For me, listening is the easiest. I really don't have problems if the one isn't specific. ( like the one you mentioned National geography can be very specific sometimes but I just understand that their words as it is maybe it's same for native English speakers.) the problem might be you do need a certain time to get used to it. I've been listening/watching them since I'm very young. I don't know much about other languages but many languages have more pronunciations than English, so I would think that probably English isn't the one difficult to understand listening compare to the others.

If you can find the English words in the dictionary, it is not the problem. We speak English with the words that are not in the dictionary. In the movie " dark world". You may heard " friends with benefit". This expression is not in the dictionary, it means friends with sex behind the scense. But, they are not in the boyfriends and girlfriends relationship. Learning English in School is the training to be an expert in English. However, picking up the English language from the people who you are dealing with in your daily life is the way of native learning. Thus, there are two ways in delivery the English language, the expert/professional form and the native form. News, Documentary are delivery in the expert/professional form. Movies,TV episodes are delivery in the native speaking form.

French can be tremendously difficult because so many words and phases are similar or identical sounding. Mon pere est tailleur. Mon pere est ailleurs. Ma sacre toux! Massacrez-tous! (Supposedly, there was a famous incident in which many unarmed civilians were shot after this off-hand comment about coughing was misheard as a command to open fire.) Admittedly, English is not much better. Since you say you find the problem to be much worse with movies, do you find the speech of some charactors significantly harder to understand than others? One of the prime dificulties of spoken English is the countless dialects and colloquial variations. News and documentaries tend to use a more standard English, but any strange variety of English might be seen in movies.

I have no problem of listening to the spoken English, writing is a pain in the neck, grammar, grammar, grammar.