Why is that new movies are reposted again? For example GI Joe, Orphan were previously posted then they were brought back again.

I'm not entirely clear on what you're asking.

If by "brought back again" you mean the thread title appears at the top of the forum thread listing, that's due to the way the forum works. Anytime a new post is added to a thread (someone posts new links, someone says thank you etc.), that thread jumps back to the top of the listings.