thanks for posting your problem.
First of all, I think you mean 5 gears
About the lights problem: you'd like to have the left hand lights switch to kill the lights?
I tdon't think this option is normal behaviour for a Kreidler.
The actual switch behaves as follows:
- horizontal position for normal lights mode
- upward position for a 'beamlight flash'
- downward position to lock into beamlight mode
The rear light is best checked if you have some spare electric wire and connect the source (the yellow cable engine connection) straight to the headlight, and from the headlight straight to the rear light. Don't forget to connect the ground cable too. If this works, then you know there's a bad connection in one of the original cables going to the back (either the yellow cable which turns grey going to rear light or the ground connection).
I hope this at least helps somewhat...
Can't help with the gears problem.