You need to edit the title to something more descriptive, and you might want to visit the rules.
For the layers issue, you need to flatten the image before you save it. That would be the Image menu, and select "Flatten" (or CTRL+Shift+F at the same time). What is happening is that your image is being saved as a Paint.NET file instead of something else. When you save the file after flattening, you can then choose the file format to use (JPG, GIF, PNG, or whatever you prefer).