So my telephone cable from the demarcation point to my apartment is broken and there's no way to get a proper technician to fix it in the next few weeks. So I tried to do it myself, but the router keeps blinking, indicating that the connection isn't functional.
I made some pics from my phone to illustrate what I did. In this first picture, there is a little Telecom box which the Telecom technician connected. This is right at the demarcation point. Instead of plugging the telephone cable in there, I cut the wires and connected them to a telephone cable. This can be seen in the background. Its a 2×2 telephone cable, but I only connected the white and red cables. The second picture shows what I did at the other end, in my appartment. cable then goes straight into the router, but without any effect. Does anyone have an idea how to proceed? Would it make sense to get a Multimeter to detect it there are some voltages measurable, or is that doubtful even it it works? Any advice is appreciated. 
Best Answer
Step 1: Bring your router to the demarc point and verify that it works there. You did not mention if you had done this, but if not, you should, as the whole point of a demarc is to say: "If it does not work here the provider needs to fix it. If it does work here the problem is in your wiring." So you need to test that.
THEN you can start to concern yourself with the wiring onward from that point. Which appears to bear no resemblance to the North American standards I'm familiar with...