hello 
i have a comment on lesson 53 :
it took me some time to realize that the first part of the text (formal ) does not correspond to the audio file :
on the written text the imperative  tense is used at the 3d person : presumably because the speakers give each other the "usted "  formal speak.... mire , ve 
however in the audio the second person   mira , ves  
presumably because the speakers are using a more casual form, giving each other el "tu " 
but i thought it should be clearer in the lesson 
unless i misunderstood 
hasta pronto 
paul