No fuel at fuel filter but can't tell if pump is getting power, everything is in german

It sounds like you may have several problems. If you cracked the fuel filter line loose and you have no fuel at all that means you are either out of gas or have an internal leakage problem. Generally the fuel accumulator will go bad(3rd component at fuel filter/pump package).There is also a check valve in the pump or the fuel injectors have been known to leak the fuel pressure down. As far as the fuel pump you should be able to have someone sit in the car and turn the key to position 2 while you listen at the rr of the car to hear if the pump comes on. During start up it only runs for a few seconds to build up fuel pressure before engine fires up. There are 2 wires on the pump. They will be marked + and -. Take a volt meter and run one lead to + and the other to a good ground you should have power at all times when the key is in pos. 2. Next put a lead to the neg. and to a good ground and see if you have volt. Remember to cycle key because the relay will only run pump until pressure is good. Pumps have been known to fail and eat up voltage. See next if the continuity changes with an ohm meter on the ground side when the key is off. You should have an open with key off and a 1 to 3 ohm circuit with key on. The fuel pump is located behind in the rear firewall.there are 2 black relays one labeled klima(climate control) the other is the fuel pump relay(it may say kick down on it because it also grounds the knockdown sol. at the transmission). circuit 30 is hot at all times and circuit 87 is for a consumer(fuel pump) you can take a fused bridge sire and bridge circuit 30 and 87 and the fuel pump should start running and you should be able to start the vehicle. If this is the case replace the relay. As a general rule of thumb I usually do the pump too but I know they are expensive.Good luck I hope i have been helpful.