Arduino Pro mini 5V and SIM800L wiring?

I have a mini A6 GA6 GPRS GSM

I followed this tutorial:
https://www.ayomaonline.com/programming/quickstart-sim800-sim800l-with-arduino/

The SIM800L module should opearate using 5V but I am having trouble uploading the sample code to the Arduino Pro mini (5V) when the SIM800L is connected to to the arduino pro mini.

When I have:
SIM800 5v ↔ Arduino pro mini Vcc
SIM800 "G" (either one) ↔ Arduino GND
SIM800 UTX ↔ Arduino D8
SIM800 URX ↔ Arduino D7

Code wont upload. If I remove the connection the code uploads to Arduino pro mini OK.

What is the right way to connect Arduino and SIM800L?

After couple of days searching this tutorial got it working:

So what was the difference? What change did you have to make?