i would like to know how the circuit work ....

 

Your schematic is almost unreadable, but it is an extremely over-designed reversing switch for a small motor which is controlled by a logic input to the base of the NPN switching transistor.

Why not just put a single resistor in series with the relay coil to reduce the 9V supply to 5V to power the relay coil? (Get rid of the regulator chip and all its bypass capacitors).

Also unclear, what is the source of the 3V that powers the motor?

 

i have upload the same pic clearer now ......

 

Our OP doesn't understand.

He is trying to make a toy car go in the reverse direction when a SPDT switch on the front of the car contacts an object, or in the forward direction when a SPDT switch on the rear of the car contacts an object.

The easiest solution would be to use a double-pole double-throw ON-ON switch (slide or toggle) wired in crossover, with a rod or beam through the entire car, connected mechanically to the slide or toggle switch handle.

A more complex solution would be to use a DPDT relay that latches with the switches.

However, now it's getting ridiculous, with a 2nd power supply, regulators, etc.