Hello Dagmar,
The error indicates that a core database table related to Joomla’s Smart Search is missing.
To fix this:
• Go to System → Maintenance → Database → Fix in your Joomla backend. This will attempt to recreate missing tables.
• If that doesn’t help, you may need to manually recreate the #__core_log_searches table via phpMyAdmin or disable the Smart Search plugins if you’re not using them.
• Or you can try re-installing joomla, It may fix this.
Let me know Is It help or not?
Best regards,