Hi there!
Lot's of help now 
Thanks a lot!!!
I've got all users and passwords written down in a password safe, so no problems with that.
BUT, i just figured out that there are some problems with the ubuntu version and the hypervisor i'm using.
I need to setup a new database host with a different ubuntu server version.
I'm doing it right now, so expect some reply the next hours.
With the new database host, i'm going to try your advice and report back.
Again, thanks a lot for your help!
in addition:
On the old database host, show grants for the openfire database user returned:
GRANT ALL PRIVILEGES ON `openfiredb`.* TO 'specificuser'@'xxx.xxx.xxx.xxx' WITH GRANT OPTION