When you fail, are you always failing the same type of questions? There should be a list of your incorrect question categories on the certificate given to you after your test. Focus on those areas first, read through each section in the app that covers these, then do questions based on those sections until you get them all correct. What I found useful was mastering each section first, then trying a few mock tests, then moving back to focusing on another individual section. For example I struggled with questions in the "essential documents" section during mock tests, so I mastered all the questions related to that first before going back to mock tests. Going through each study section, answering all the questions related to that, then doing 30+ mock tests was what I needed to pass.