A good place to start learning might be this book:
A fact that may make your searches for answers easier is that the programming language is called R. RStudio is a program that is separate from R and provides many convenient tools for writing R code and viewing the results of running code. It is possible to use R without RStudio, though I definitely recommend using it. Most of the problems you encounter will concern the R language.
Also, there are usually many ways to do any particular task with R. The book I recommended emphasizes a particular set of tools called the tidyverse. If you search other sources, they may use other methods. It is easy for beginners to get confused by by the variety of methods. Some confusion and frustration are inevitable when learning but feel free to ask here when you get stuck on a problem.