Friday and Monday closed as they are public holidays, Saturday open, as said, but I don't think that the shops will be empty on Saturday. That's an urban myth that makes people go crazy on Thursdays, so it is true that people will go shopping big time on Thursday (and behave as if there will never be food sold again)

However, we're meeting up on Thursday anyway, I'm going to Metro before our meeting, that's a huge wholesaler, originally for distributors, but I have a Metro card and can bring one extra person. So if you like you can join me

Normally I would say be prepared for a consume shock, but it's probably still small in comparison to American hyper markets...