Someone on a different forum found the solution and i wanted to share it here for everyone who has the same problem. I had to change the timing variables in configuration.h to the following:
#define ST7920_DELAY_1 DELAY_NS(400)
#define ST7920_DELAY_2 DELAY_NS(400)
#define ST7920_DELAY_3 DELAY_NS(400)
Probably lower values will work to, i still have to check what’s the lowest value that works, but these values at least work!