Why do I have 5 wire in my wall socket?
Do NOT touch the 3 hot wires together.  From what I have heard, unlike the US, Germany provides full 3 phase power to residences.  That means those three hot wires are each 120 degrees out of phase with each other, so touching them will create a short circuit.  If you use a multimeter to measure the voltage from one to the other, you should see somewhere around 200 volts, and 220 between any one of them and neutral/ground.  Regular outlets in Europe are 220 volts, so they are only wired to one of the three phases, and neutral.  Different outlets should each use a different phase so the load is roughly balanced between the phases.