… and make sure you have spaces where spaces are needed:
Number RadiatorThermostat01_Temperature "Computerzimmer Heizkoerper Temperatur [%.1f °C]" (gMAPDB,gRRD4J) { channel="zwave:device:15a7a49f3a6:node76:sensor_temperature" }
There is one missing between your group definition and your channel definition. And don’t tell us in your actual setup the space is not missing because of a copy and paste error 
