Thread:Project:Support desk/Problem with Sideloading and Directory index/reply

The Directory index forbidden by Options directive isn't the real error here. It's just that something is referring to /var/www/web5309/html/schotterheiden/MW120x/skins/common/images/ directly through the web and options doesn't allow the contents of that directory to be listed.

The real problem is the Temporary file couldn't be created. Check if the value of $wgTmpDirectory is correctly set, exists and is writtable by the webserver.