PGP Failure - already tried everything i found while using search function!

Setup, Configuration and Use Beginners
1

Hello guys,

when i try to use apt-get update with SU i get the following failure:

GPG-Fehler: http://dl.bintray.com stable Release: Die folgenden Signaturen konnten nicht überprüft werden, weil ihr öffentlicher Schlüssel nicht verfügbar ist: NO_PUBKEY 075721F6A224060A

When i try to add this key ( wget -qO - ‘https://bintray.com/user/downloadSubjectPublicKey?username=openhab’ | apt-key add -), i got the following failure :
gpg: Keine gültigen OpenPGP-Daten gefunden.

Any ideas?

best regards

Edit: Already tried everything i found while using search function!