Now you know the Sanchez case because you have read it. But what do others think about it? And how does it fit with previus case law of the Court?

In this section, you are asked to go and do some broader research about the case. It is always easy to start with blogs - see Opinio Juris, usually there is also something on Strasbourg Observers or Verfassungsblog . If the case is not too fresh, there might already be some academic comentaries - just try to google around, using the case name, case number, or even some keywords.

Another quest is to look into previous cases on similar issues. Here, HUDOC can help you a lot: just see the "Case Details" sections when you have found the case: https://hudoc.echr.coe.int/eng?i=001-211777

Spend sufficient time on this. Read texts and cases, take notes, think. Create an overview of all the relevant academic information you were able to find (including the academic blogosphere) and submit it when you're ready: