Welcome! Smartthings is very powerful, but not very intuitive. Do feel free to ask any questions in the forums and someone will try to help.
You will need the new app (“smartthings (Samsung connect)” or STSC) to set up your new hub, but after that most people prefer to use the classic app for now. See the following (this is a clickable link)
Meanwhile, there are quick browse lists in the community – created wiki which can help you more quickly find things in this forum, because the search here isn’t very good.
In particular, if you look down near the bottom of that page for the “project reports” section and then choose the “get started“ list, you will probably find quite a few topics that will be of interest.