Now I have updated. I could not use the update function in Components, because there were some errors. I have downloades the update package and copied it via ftp.
The error with the image at the article tab goes on and the title is missing.

Could you remind me what the initial issue was?
Also..

could not use the update function in Components, because there were some errors.

That also does not sound good. Can you please describe these issues?

Hello Mr. Boghossian,
at first thanks for your attention.
After Updating to 3.1.1 Joomla-Installation seems to be korrekt, the update says:
"Joomla ist aktuell". That's ok.
There is only the language plugin, which makes mistakes now, please look at the screenshot.
My site is: www.fewo-stpeter.de
And there is one error more at the kontakt-site, but I don't think, thats an error from K2.

The K2-error is still the same, that I can't add an image to an article.

I loaded down the language pack for 3.3 and tried to install it.
The error was:

Warnung

JFTP: :store: Unerwartete Antwort

Warnung! - Die Datei kann nicht verschoben werden!

JFolder: :files: Der Pfad ist kein Ordner! Pfad: /home/strato/www/fe/www.fewo-stpeter.de/htdocs/spo_nordsee/tmp/install_53aae7e684e50

JFolder: :folder: Der Pfad ist kein Ordner! Pfad: /home/strato/www/fe/www.fewo-stpeter.de/htdocs/spo_nordsee/tmp/install_53aae7e684e50

JFolder: :files: Der Pfad ist kein Ordner! Pfad: /home/strato/www/fe/www.fewo-stpeter.de/htdocs/spo_nordsee/tmp/install_53aae7e684e50

JInstaller: :Install: Die Joomla!-XML-Installationsdatei konnte nicht gefunden werden.


Fehler

Archive does not exist

I don't think that it is a K2 problem, may be its the reason for my K2-image-problem?

It could be a permission's related issue.

Right permissions on all joomla sites:
755 for folders
644 for files

Please install Admin Tools from www.akeebabackup.com/downloads/admin-tools.html in order to fix your permissions as they should be.

In any case you should contact your hosting provider about this issue because it might be caused by a number of factors.

Thanks for your answer.
I tried to install AkeebaAdminTools - of course the system showed the same error.
So I unzipped manually the files into the tmp-folder and installed it. AdminTools are running.
Under Tools I set the preferences and tried to install another component. The error goes on and the K2-Articles got no image.
I called to my provider and asked him for the erros. He made a look at all folders and files and told me they are all set to 755 / 644. He will aks his technicians for more and in the next days I shall get an answer.
When I got more information I will post it here.
Have a nice weekend.
G.

You too Godber,
What you can check for yourself is a common misconfiguration error.

Open your configuration.php and make sure the /log/ and /tmp folder paths are correct.

Hi, Mr. Boghossian.
After your answer I tried to find out the path-settings and so on. My Provider has an own path-structure, so couldn't change anything. Trying several days. At least I changed the provider, that uses time. But now it seems all is going right.
Thank you for your help.

You 're welcome Godber :)
I 'm glad that the issue was resolved.