@Adam Engst:

Thank you very much for your advice! The iphone of my son didn't charge. The lightning-plug didn't fit anymore. He tried to clean the adapter just by blowing very hard on the connector. This didn't work. So we ordered a new adapter and tools. But after reading your note I just took a very small and thin screwdriver and scratched the bottom of the adapter which brought a big amount of fluff and fuzz back to daylight.

Everything is fine again. So your tip prevented us from some serious distress. Thanks again.