but the car i going backwards and forward to quickly, is there a function or a code that i can use to make the car go forward a little bit slower ?
The analogWrite() calls in Stanga(), Dreapta(), etc. are what define how fast the motors spin. Change the 128 to a smaller value to make the motor spin slower.
The speed that the motor spins, sitting on the stand, and the speed it spins actually moving the car will not be the same.