can someone help or guide me to how to get this installed. Sorry for the stupid question but I am quite knew here and the only documentation I Could find on the GIT is:
Install directly from within your Nextcloud from the app store
Clone this repository in you Nextcloud app folder
But how? I do not find anything in the NExtcloud Apps. And why Cloning afterwards?
cd <nextcloud-folder>/apps
git clone https://github.com/rullzer/previewgenerator.git
chown -R www-data:www-data previewgenerator # or whatever the webserver user is