It's been a while since I've handed in my portfolio but if I look at the requirements the most important thing to do when applying for an expert certification is to demonstrate what you did as an expert. I saw this list of topics you need to demonstrate in the project you will be refering to:
Make sure to demonstrate how you handled each topic and elaborate on the complexitity you have faced and how you solved it.
Try to incorporate these topics in a flowing matter so that it's also nice to read for your assessor :-)
Hope this helps! Give me a call if you would like to discuss this in more detail!