Hi Mourad,
The scoring algorithm on the Official GMAT is far more complicated than most people realize - and it takes into account a number of different factors (far more than just the number of correct/incorrect responses). As such, you shouldn't be wasting your time trying to figure all of that out. Since that algorithm is proprietary, no GMAT company has an exact match for it, thus CAT scores can vary a bit based on the 'biases' involved in their respective designs. Assuming you took this CAT in a realistic fashion that matches up with what you'll face on Test Day, we have to assume that the result is accurate.
Many Test Takers face pacing problems while dealing with either the Quant or Verbal section (or both) at some point in their studies - so you're not alone. Pacing problems don't exist on their own though - they're the results of OTHER problems (in simple terms, "your way" of approaching the section is causing the problem). To solve all of these problems (pacing, accuracy, score, etc.), you have to focus on learning and practicing the proper Tactics - so that you can approach each prompt in an efficient way.
GMAT assassins aren't born, they're made,
Rich