Hi, thanks four your reply.
Yes I can still charge the phone and the LED is working.
The problem is the power button as it already wasn’t possible for some time to wake up the screen using the power button.
I tried the cleaning, but this didn’t immediately help.
I am able to enter the Fast Boot Mode by holding Volume down and inserting while plugging the cable in. But I could not use it, to boot the phone, as the power button is required to select start.
I somehow managed to boot it accidently with a random combination of Volume up and down presses while connecting cable.
I have now activated USB-debugging in the developer-settings, as according to some guides this would allow booting the phone from a PC using adb commands.
A DIY repair is not possible, as the Volume/Power button module is not sold separately, I’m therefore forced to send it to Fairphones repairservice to get it fixed. However neither the price list, nor the customer support itselfe will say anything about the estimeted costs.