Sour espresso [Bezzera BZ10 Mahlkonig X54]

I recently started with espresso. I have bought a Bezzera BZ10 and Mahlkonig X54 but after dozens of tries I can’t get a decent shot of espresso.
I have ground course, I have ground fine and read every article I could find but whatever I do the pressure does not come above 5 bar, the espresso reaches the goal output weight within 15 seconds tops, but most of the times faster, and the shot remains extremely sour.
What am I doing wrong and how can I fix this?