I really, really want to complete this model, but I have no idea as to how to proceed from step 7 to step 8. I know I must collapse the folds somehow, but I don't know how to do so step by step so that it could end up looking like step 8. Is it possible for someone to post a short video or take step by step pictures so that I know how to fold it?

Sorry for being so lacking in my ability to understand this model.

Here is the model: http://pajarita.org/diagramas/files/intern1-1.pdf

Thank you in advance to those who will help me.