My first time ever in the USA, could someone help me?

Hi! I’m from Europe, and I’ll be coming to Chicago in the first weeks of September. I’ve never been in the USA, I might need some tips.

Does anybody know a place to stay? I’ve looked through many booking sites and it’s really really expensive.
If someone knows a hidden jem please let me know, I would really appreciate it.

And also, what main things are there to see? I don’t know much about Chicago and from online videos I still don’t really know (except the big steel lightning bean)