What you're describing sounds weird...pictures might help.
There shouldn't be a decompression valve on a Puch. There should be a single cable running from the large black lever to your gearbox. That engages the clutch and lets the pedals turn the engine over. Turn the run switch (there should be one) to run, turn the fuel valve on, pull the clutch lever and pedal. If everything is working properly, the engine should start (might take some choke). If it doesn't, you have a problem(s) somewhere that you need to fix. Check out Fred's Guide in the Resources->Articles section.