I finally paired them. You will have to do it in DeConz and not in Phoscon.
In DeConz head to the menu, click on Panels and activate control:
In the control tab you have a DDF tab a Pairing tab. First you check the Bronze option and activate hybrid mode in the DDF tab:
Then you switch to the Pairing tab and activate join permit. Now hold the pairing button of your Aqara E1 door & window sensor for like 5 seconds until a new node shows up.
That means it’s finalley paired and you may head over to Phoscon where the sensor should now appear in the sensors list. In order to make them show up in HA you need to restart the Deconz integration (not the addon).
Hope this works for you as well as it has for me.