Did you add the typo in Maqketplace or is that the real error message? If so maybe check if there is a plugin directory with the name Maqketplace

@sgiehl There is no directory named Maqketplace and matomo worked fine for several months before :/

EDIT: This is the actual error message - no typo

I wonder where the typo comes from. It's not included anywhere in Matomo source. Maybe try reuploading the source files...

@sgiehl I searched through all MySQL tables and checked all files with grep - no string like Maqketplace. Any idea where this came from?

It seems to have all started with this line three days ago:

AH01071: Got error 'PHP message: PHP Fatal error:  Interface 'Zend_Db_Statement_Interface' not found in /var/www/vhosts/matomo/httpdocs/libs/Zend/Db/Statement.php on line 42\n'

@sgiehl I've reuploaded matomo's files and everything works fine now. Was my matomo hacked?

Was my matomo hacked?

We are not aware of any security breach in matomo that would allow changing any files in latest version.
But if you think it might got hacked it might make sense to change your passwords...

Ok thanks then :)

This was the very first error:

Matomo encoutered an error: Class 'Zend_Loader' not found (which lead to: Circular dependency detected while trying to resolve entry 'Piwik\Plugins\CorePluginsAdmin\Controller')

UPDATE: Files from my installation don't differ from the latest matomo 3.4.0 files (besides tmp/ of course) :)