Hi Mahdi,
I'm not sure you refer to a full mock exam. My recommendation would be to start with some timed quiz, so that you have the opportunity to practice with less questions; time will be adjusted accordingly.
Another thing I noticed when I was using the simulation is that - if I wasn't sure about the answer, or even had no clue about it - it didn't help to keep reading it and thinking about the possible answer. Instead, if I flagged that and came to that later, I was able to notice some details or hints that I previously overlooked. Sometimes even other questions will be helpful to guide you through the correct answer.
Hope this helps,
Gabriella