I tried 2 times before to learn driving at driving schools. I feel some improvement at first and so I feel worse and worse. I think my problem is that I m v afraid when I am on a high speed ( I mean more than 40 kph) to make an accident.
Maybe, I ve a physical problem that I can t ve a mental muscle synchronization (frogive me if I use the wrong word. But I hope you get it), in other words, I mean I can't take the needed immediate reaction when I m driving when I should stop or decrease speed or dodge any thing.
I used to learn with manual cars and I found it s v hard to make gear box transitions according to the speed.
Now, it s a problem for me that I can't drive I ve a family and go to work everyday by public transportation.

Driving is a learned skill. No-one is born being able to drive. Get proper lessons from a qualified teacher, and spend a lot of time practicing on safe areas where there is no other traffic or pedestrians etc.

And don't obsess about it. Remember, in a city, it's very unlikely you will ever go over 40kpm anyway.

Eileen G gave you some great advice.

Driving anxiety is more common than you think. In some of the big cities they even have driving education teachers who's specialty is driving anxiety/phobias.

If all else fails, you might consider talking to a counselor to get to the bottom of your fear.