RX and TX for Arduino Mega is not working

Hello Friends, i need help please

I bought arduino Mega and i try to communicate with my SIM800l but is not responding, any help please.

Regards.

you come up a little short on detail

read the bottom half of my signature line

come back with a copy of your sketch, posted as described in those instructions

you do know that you connect TX on the GPS to RX on the Arduino, and vice versa?