Guillaume's place is great and actually much more spacious than what you'd think based on the photos. It's located in one of the best neighborhoods in Lisbon - Principe Real - just 2 minutes from a supermarket and the amazing gelateria Nannarella.
The apartment is on the top (fourth) floor and thus gets a lot of natural light. At the same time, it's easy to make it dark to sleep because of the shutters in front of the windows.
More than anything else, I was to emphasize what an amazing host Guillaume is. He wasn't in Lisbon when I arrived but had a friend of his, Paulo, welcome me. Both he and Paula were super quick to respond when I had questions and when an issue arose because of unannounced works in the street, Guillaume went out of his way to help me. I truly cannot recommend staying with him enough. He'll do everything in his power to make sure you feel comfortable while you're in Lisbon.