The file components/com_cjforum/tmpl/topicform/default.php exists

its been a completely new Joomla 6 Installation in my case too.

i have attached a debugging image, maybe it helps?

I could not reproduce this. I created fresh Joomla 6 installation and installed the package. Can you check if the file components/com_cjforum/tmp/topicform/default.php exist?

But if I go in Frontend to CjForum > Dashboard > Start Discussion it gives me the following error:Page not found
Bei Problemen ist der Administrator dieser Website zuständig.
404 Viewnot found [Name, Typ, Präfix]: topicform, html, site