Hope this is the right forum for my question.
I have formatted my harddisk of my iMac pc.
I reinstalled Arduino and the ESP8266 library.
When I try to upload the code to the Arduino, the serial ports are greyed out.
I have used several USB cables, but nothing works.
I hope somebody can give me some help how to procedure.
Thank you in advance.
Yvonne
Problem solved finally.
I installed the SiLabsUSBDriver and followed the instructions.
It works: /dev/cu.slab_USBtoUART.
Hopefully this will help somebody else as well.