I have problems with either my Arduino or my OLED screen because after using that tutorial:
I uploaded a program attached to that tutorial and nothing shows up.
I double checked my wiring if it is correct, I connected all wires exactly like in the tutorial.
The tutorial is for a Nano. If you make the connections shown on the Nano diagram but with a Leonardo it won't work because the SPI pins are not the same on the Leonardo. Refer to this page of the Arduino documentation to see the SPI pins on the Leonardo:
That was actually the first thing I tried after finding that I should connect it to ICSP pins, but after first wiring it didn't work so I thought it cannot be that easy, and thats why I wanted to "bypass" the pins I was sure it doesn't work. But now I tried and it is okay, probably faulty wire.