Hi Jacek, welcome to the madhouse!
First off do you have a wiring diagram? if not go to the thread "Wiring diagrams" on this forum there should be one there that covers your bike.
Do you have a multimeter? If not get one they're not expensive and will save you a lot of time and money in time.
Do your cables run through the handlebars? Makes tracing faults a bit more tricky.
Start with the switches and using your multimeter and wiring diagram test each one for correct function, hopefully they are then let us know how you get on.
Loki
