I have some issues when it comes to download on arduino.

What does: "avrdude: stk500_getsync(): not in sync: resp=0x00" correspond to?

Thank you by advance.

Nice thread title.. Google the error message and you will find the solution.

Remove the '328P and try the Loopback test (directions located in this forum). If that doesn't work, the USB/Serial interface is not working. If it does work, the '328P is not working. Folks have reported success using a Programmer to reload the parts.