how can i fix the error ? stk500v2_getsync(): timeout communicating with programmer
It's our old friend the CH340G again, isn't it? 

You've been sold a dud, I'm afraid. The USB chip used there is dead. It happens a lot with those cheap Chinese boards. You should still be able to use the board with an external FTDI adapter by wiring it in to TX->RX, RX->TX and DTR->RESET (via a 100nF capacitor) with power and ground connected of course.

There is also a slim chance that the CH340G may interfere with the TX/RX pins, in which case you may need to remove it. Simply cutting the pins on it with an xacto knife then removing the stumps with a soldering iron and tweezers would do the job.