aaaah perfect, thank you! so i see, HIGH is like on and LOW like off in this case.
so theres one last question, just to understand this correctly. i cant get rid of the datasheet of the ULN2803. 
what goes in and what comes out? (amperes and volts). so am i going to connect the arduino to pins 1-8 and pins 11-18 to the rows of the matrix, and for the columns i use resistors to get
the correct amount of volts, right?
thank you very much again! this is so much fun for me and i like to learn mew
things 