I´m trying to unpack the exercise system but unfortunately something seems to be wrong with the file (screenshot states unexpected end of the file + data error)). I have downloaded it twice now, MD5 checksum: 32aab0f450970e338768b2e1ba63f385, SHA1 checksum: dbbd6ab22d0aaca8f76da74e5132c673219ebf38.
Strange. Just tested it myself once more and it still works for me. Since the 7-Zip test failed for you it must be your download connection. I would recommend you try to download and test the archive once more using another machine.