yes, it was missing. I don't have this file under the /mnt/conf/etc. Because of that I've done a
sudo find / | grep skylark_config.json
The find command list up all files on the chip but with the grep it only shows me anything that has skylark_config.json in its name. Then I found the File /etc/skylark_config.json. I opened it in the VI editor (i hate this editor ) and it looking after the lines with the code on zoltan's post. Then I edited only the numbers in the Custom section. Saved the file, doing the sync command to write onto the CHIPs flash and opened the file again and checked if its saved. After reboot, it gots overwritten.
Then I do the same again and then opened a blank skylark_config.json under /mnt/conf/etc/ and only copy and paste the custom section (i know I'm dumb and eventually have to copy the whole file. But I forgot this.) in the file. Saved, do the sync command, rebooted and now nothing happens.
I've started the CHIP now and it blinks. But the WIFI doesn't come up and over USB I get a CDC Composite device.