This is caused by the site missing SSL certificates. To fix this, visit https://orange.informatik.uni-stuttgart.de/graphql and accept the "unsafe" warning of your browser there. Afterwards you can return to the site and after a refresh everything should work.
This is caused by the site missing SSL certificates. To fix this, open your browser's developer tools (F12) and go to the console. Then, again try uploading/viewing a file. In the dev console, a CORS error with the URL of the file you're trying to access should be printed. Open this URL in a new tab and accept the "unsafe" warning of your browser there. Afterwards you can return to the site and after a refresh all media files should be accessible.