@Francesco2017, Hi, welcome back to the forum!
Maybe it is time for you to read (once again) How to get the best out of this forum.
Now we know which library you use. But we don't know which display you selected.
And we need to know the exact display you have; please post a clickable link.
And tell which processor/board you use and compile for.
Your code looks ok, but maybe your display panel is not supported by GxEPD2.
The panel usually has some inking on the flex connector. Please report it, then I can compare to the panels I have.
The list of methods can be found in the header files of GxEPD2 and in Adafruit_GFX.h
Jean-Marc
BTW: You will get garbage (scrambling), if you print a value that is changed inside the page loop. Every run through the loop needs to print exactly the same!