Hi there!
Excel and Postgres are two different tools/technologies serving different purposes and targeting different users. Excel is best for GUI, where users can enter data and apply formulas. It is usually good for day-to-day use. It provides excellent reporting. Postgres, is a database, usually running on GUI-less servers where pretty dashboards are not an option. There you have to use the command line but very carefully. This doesn’t mean that there is no GUI for Postgres. Check the tool dbeaver for instance, there you can see tables, data etc.
Yes you can refer to this post.
Check out the official documentation of Postgres.
The course is still in beta, and feedback is welcome. Kindly refer to other forum posts as well in case you run into issues.