Serving images from Google Photos will make users load content from Google servers.
Managing Google Photos in the Event Gallery backend will call Google services as well. Your backend users data will be used to call those services like the Album Selector. If you use private albums, a Google Auth Token is necessary. To create this token, your browser will use Google services as well as calling www.svenbluege.de. To fetch album data with that Google Auth Token, a connection to www.svenbluege.de is made as well. That is necessary to obtain an temporary additional access token for Google Photos.