Mahoud,
A great big congratulations on your exam success!! We at OSP really appreciate your positive feedback and any advice on how we can improve our products. Continuous improvement by listening to our customers has been a cornerstone of our success. Thank you so much for sharing your success with us, it makes our day!!
Yes, I believe our tests are a bit more difficult than some of the others and I echo what you said, if you are scoring in the 70-80 % range on our questions you
should be good to go in your PMI-ACP exam. You did the hard work of preparing and you earned your success! We agree that until the Agile Practitioners Guide from PMI comes out later this year or early in 2018, PMI-ACP Exam Prep by Mike Giffiths (from RMC i.e. "Rita") is the best prep book available for the exam.
So relax, rest your eyes and mind, and celebrate.
Congratulations sir!!