Question about Logitech Z533

Good evening I recently bought the Z533 at Media Markt. My PC has a green output at the back, a blue and a pink one and a headphone connection at the front. I have tried everything and only the right and left boxes work and I have also turned the knob but there is also no noise if you listen very closely there is a signal but like a crackle but then it can't be broken on the mobile phone I have already connected it there is also nothing happens does anyone have any advice?... The purchase is also a little longer ago unfortunately... I just don't understand that when you get something, you assume that it should work.