As a Mendix developer you are expected to study and understand the platform. Thus for the Mendix certification to mean anything its exams must be done honestly, meaning no stolen copies of there exams. It is also illegal to have copies of Mendix exams as it is the property of Mendix and they don't hand it out.
So study by doing the learning paths under the academy tab, register for the exam under the certification tab and then good luck with the exam. For info about the exam please look at the certification tab.
Just go through intermediate learning path, and do it honestly, also go through this link MendixIntermediateClosedBookExamGuide-v2_1.pdf (dropbox.com) you will get idea what topics to cover and exam guide.
All the best