The only problem is that natural speech it isn't. Language of films, documentaries and sitcoms is scripted: packs of young(ish) things with university education toil to produce "lines" which would present their characters as especially romantic, or tough, or witty, with no effort spared (especially in case of much cruder sitcoms) to turn every second line into a "gag" (doused with gallons of canned laughter).
Sitcoms being the worst offender by far, besides being quite crude, also paint a misleading picture of life in an English-speaking country, which would land a hapless foreigner in jail, literally, within hours, if he tried to follow the example of sitcom actors in his speech or actions in real life. It is incredibly unrealistic.
THEREFORE a question arises - are there TV shows which present more naturally-sounding unscripted language in more realistic situations? Without as much distortion of life?
One possible idea would be to try "reality TV" as a genre. Scenes might be set up, but at least language is no longer scripted. But generally, I am at a loss here and do not know good examples.
Could someone suggest any solutions? And you do not need to agree to my premise that films and sitcoms are unusable, so feel free to defend them and prove me wrong(and you'll have on your side at least some academics in the USA who deemed it valuable to collect the language of sitcoms into a "corpus" (which is available freely on-line), considering it to be a bona fide representation of "very informal English".)