The R learning curve was tough for me, but worth it. Here are some resources that I found invaluable in learning R to facilitate my data science, stats, and open science practices, and most of these continue to be go-to resources.
R for Data Science (Hadley Wickham)
Multilevel Modeling using rstanarm
Best Practices for Writing R Code
Google Developers Videos for Learning R
Fox and Weisberg (this is the companion for the well known car library)