So, I'd got a pair of cheap earphones that broken after a while (Left ear is no more receiving sound). I defined the problem: it's some broken wires after the button. The thing is that I cannot figure out what goes where.
As you can see in the picture, there are red, blue, two copper (my first guess is that they're ground) wires. Short notice: the whole picture is of the wire that goes to the left ear.
I have connected blue with blue. When I touch the microphone with one of the copper wires, my smartphone switches to the previous song (or lets music go to the left ear as well). I have tried connecting the three copper wires (one from one end, two from another) together. Music seems to be playing fine. So, my questions to those who already did it at some point: which wires to connect and where to do it right?