SIM800L EVB Not working

I bought a gsm module, and I wanna connect it with Arduino but I have a problem.

I linked gsm SIM800L with regular LM2596 12v 2A I changed tension to 5v, So far the gsm is working. but if I connect TX_ARDUINO with RX_GSM the module entre in the loop of the restart. the picture explain the montage

From Using SIM800L

We cannot directly connect Rx pin on module to Arduino’s digital pin as Arduino Uno uses 5V GPIO whereas the SIM800L module uses 3.3V level logic and is NOT 5V tolerant. This means the Tx signal coming from the Arduino Uno must be stepped down to 3.3V so as not to damage the SIM800L module. There are several ways to do this but the easiest way is to use a simple resistor divider. A 10K resistor between SIM800L Rx and Arduino D2, and 20K between SIM800L Rx and GND would work fine.