Hi Oliver,

Sorry for maybe stupid question, but I want to be sure.

Are you trying to install Quckstart inside current Joomla (what is not possible!), or in normal way you unzipped all and you are installing it step by step like Joomla core.

Guide for beginners: https://www.joomshaper.com/documentation/joomla-templates/investa/quickstart-demo-installation

PHP version must be 8.0 or 8.1, not above that.