Welcome to the site and the community, We love Chicago and have dear friends there. Could never live there due to the weather but that's another story.
May I suggest checking out Youtube videos called "talk the streets" with Liz. Her short videos are free, practical and easy to understand. She will have you speaking like a native in no time. There are quite a few videos available, try to start with her first lesson, "sounding like a local."
On this site there are a lot of expats with a lot of experiences who can help you along your journey. Some things have changed since we arrived here from Kentucky, pre-covid such as immigration requirements etc. But there are other things to read that will never change such as learning to drive here as an American.
For up to date requirements on the paperwork needed, you can check out the Portuguese embassy site (in Washington DC) https://washingtondc.embaixadaportugal.mne.gov.pt/en/consular-services/visa-information
But you can also ask other expats for help with questions. I am happy to try and answer your questions.