Hi everyone!
I've transfered the circuit using another laptop and it works pretty well (I've of course followed your diode advice Markt even before the crash of my laptop).
I knew that the arduino works better between 7-12 V but I didn´t expect the regulator would get so hot with 14V (yes, it's 14V ant not 13V while the car is moving 
). So I'm going to get a step down regulator 14V -> 7-12V (9V if I can found). Thank you for the advices guys!
Have a nice day!