Extracting the data from a radioButton

Observe differs from observeEvent by not having a first param which details what event(s) are rhe trigger.
Im sorry but there's no alternative to learning shiny than studying it. The documentation for shiny online by rstudio is very good and explains observe, observeEvent etc in great detail.

Also, debugging shiny is a complex skill. I think that after covering the fundamentals you can look at this guide.

(Shiny debugging and reprex guide)