Moin,
i think libsecure will be the reason. You take a short test if you disable the extension for a short time and do some clicks on the page. I think this will be much faster after that.
But if you disable libsecure it is possible to get XSS attacks in Knowledgeroot. So what can you do. You have 2 filters in libsecure. Open config.php in the extension folder and disable the whiteliste. The blacklist works much faster. The whitelist is very heavy so this will be the reason why it is slow.
So disable the whitelist and it will be faster

regards,
Frank