Of course, to understand speech, it is necessary to know at least 75%-100% of the regular, non-specialized, English. If your language is not up to the desired level, it will be very difficult to distinguish, even everyday English. So first of all you need to improve your English.
Many, believing that their English is at a sufficient level, rush to watch English films in the original without subtitles. And then in frustration quit trying to learn to understand English by ear. The fact that in the phrases in that language some words can merge into a strange to the ear design, so don't tell me where the word starts and where it end. Therefore watch English movies best with English subtitles. So all of these long chains of words immediately disintegrate into understandable components. If you are not confident in your English level, start with children's cartoons. And for starters, you can start with us. The fact that Americans are slightly less inclined to collect all the words into one, at first, they are easier to understand.
Then try the Internet to find an English speaking person, it can be found on a variety of linguistic resources, in Facebook, or discussion forums. If you find this, encourage him to talk on Skype, preferably with the cameras, as any language is easier perceived by the ear when you can read the so-called non-verbal language.
After this practice, try to watch the news or documentaries with real people. If you feel insecure, help yourself with the subtitles. Listen to audio books in the English language. A good option would be "Harry Potter", read by Stephen fry, which has very clear pronunciation. And the book is written in fairly simple but colorful language.
Try to gradually disable the subtitles. The film which is good to check how much has increased your understanding of English comprehension - "Forrest Gump". The main character says slowly and very simply, the other characters in different ways, but in General is clear. Except, perhaps, appeared for half a minute in the recording of John Lennon, Liverpool whose pronunciation is difficult to understand even some English.