Does anybody know, or have an idea, of what really happened on 9/11?

I know that it is the saddest day in US history, and a lot of people died. But I think that not figuring out how it all happened and what exactly did happen would disgrace them. I’m not saying revenge, but discovering the truth.
I’m only thirteen and don’t know that much about it, but know enough to know that it is fishy and people are lying; most likely the government.
First, why did fighter planes not intercept and stop the terrorists? I heard the people who should have done that were ordered to stand down on that particular day. Who ordered them to stand down and why did they do it? They could have saved a lot of lives!
Then, the buildings would not have fallen like a demolition from a plane crash. No other building in history has fallen like that because of a plane crash, right? It was a steel building; it would have stood, wouldn’t it have? And I think building #7 fell like that, too. Somebody set it up.
I’m not so sure about this last one, but didn’t we go to war with Iraq right after? I thought the terrorists weren’t from there.
What’s your viewpoint and can do you know what did or might have happened on 9/11?