re: Spain must sees and dos?

I honestly wouldn’t spend too much time in Madrid. It’s an enormous “new city”. You won’t see a lot of “old” stuff. There are two amazing museums so if you love art you can do those. Also some great food. If that’s where your friend is located than that changed the algebra a bit and they can get you to a more local experience.

I think Barcelona and Seville are musts personally. 3 days in each would be great if you can swing it.