A note about LIS, the Lisbon International Airport. Its very small, only 2 terminals. You can get there for less than €15 in a cab (15 mins from city center) or €1.50 on the subway (30 mins). Flying within the country or within the EU is a breeze and arriving for the baggage cutoff should be plenty of time. However, if you are arriving to LIS you need to have water, a snack and an extra battery pack on you cause 2 of the 3 times I stood in the passport control line it took 1.5 hrs for non-EU citizens (which remember now includes the English). The WiFi is ok!
There is so much to do in Lisbon, I’m not going to pretend to be able to cover it all here. Much like NYC its hard to have a bad meal here, yelp works just as good as anything else. I do recommend if you are here on a shorter trip to plan 2-3 days for day trips. 2-3 days for city exploring should be ok. Everything is close downtown and very walkable, transportation is pretty cheap too. The Bolt app is great for ride sharing.