It’s hard to say what exactly is going on without more information, but seeing as you’re new to WordPress, it may just be a simple Permalink issue. When on your dashboard, go to Settings > Permalinks, and change this to the “Post Name” option.
If that doesn’t work, please provide more information. Is category an actual category, or is it a page? Is announcements a page or a post of a certain category? Anything you can tell us will help.