You can search for "the first video of postgraduate mathematics" in Youku or Baidu. This year's latest edition is serialized, and dozens or more files can be downloaded. A series of explanations are very systematic and in place. This video bookstore and supporting books cost more than 100 yuan, which is very good.
Youku has a free download. Go to Youku's website to download a download software dedicated to Youku. Then you can download the video you need.