Thank you again, perfect!
So my Matrix got red LEDs with a forward voltage of 1.8V, so this would be (5V - 0.7V - 1.8V)/0.02 = 125 Ohms. So i'm going to use 130 ohms resistors right?
So now i know how i have to connect everything, thank you. but could you please be a bit more precise about what the ULN2803 actually does? i mean what is input and output in amperes and volts?