Hi Andrei,
I can completely understand feeling disheartened after failing the exam.
You haven't mentioned exactly how you went about with practice tests prior to the exam, so that may prevent anyone from being able to offer accurate advice on what you might have missed (if anything).
However, I do believe in the power of practice. With enough practice tests, and continuous tracking of your performance, you can definitely go into the next exam feeling confident.
I would recommend focusing on time management the next time round - making sure you have more than enough time to review your answers too.
Please make good use of the "flag" options so that you can return to questions you want to review without wasting any time on them.