OK DavidM,
I really hope you're joking about this. I saw the same "documentary," and as a physicist with a minor in structural engineering, the whole premise of the movie is completely absurd. And it doesn't take a degree in physics or engineering to see that.
Their premise, that one tank of jet fuel was insufficient to bring down one of the towers (one planer per tower) is inane. It IS painfully obvious that the initial explosion of the plane's fuel caused almost NO structural damage to the main structure of the towers. It was, however, enough to instantaneously raise the temperature inside the upper 1/3 of the building over 1100 degrees celsius. And those towers were absolutely stuffed chock-full of a completely different type of fuel altogether.
Paper, wooden desks, drywall, copy machines, and even people will easily incinerate, combust and begin to radiate their own heat when subjected to that much thermal energy. This literally created a box of fuel burning at a rate that only accelerated as the moments went by.
But do you know what doesn't burn, even at 1100 degrees celsius? Steel. Steel conducts heat quite well though, and then it melts when it gets to about 1537 degrees celsius. The long steel supports of the building conducted this tremendous heat (that started out at around 1100 degrees celsius) all the way up and down the building. The "bombs" people claim to have seen lower in the building just before the towers went down were actually fires caused by the steel beams (then at about 1500 degrees celsius, almost molten) burning all of the non-steel materials around them.
The furnace in the upper 1/3 of the building continued to heat the steel beams, which were such good thermal conductors that the temperature of the beams in the lower 2/3 of the building was not much lower than the temperature in the upper 1/3. By the time the beams in the upper 1/3 melted, the lower beams were so hot that they were incredibly weakened and unable to bear the force of the top 1/3 of the building crashing down upon it.
Why is that so difficult for people to understand?
Anyway

It's obvious that it's all a lot different than ost media make us believe. But why is the US government obviously lying about so much there?
What are they trying to hide?

The movie isn't talk about that, it's really only touching facts.