How to deal with large CSV files in R (R Studio, R Language)?

Question

R

Good afternoon, comrades.
Please tell a newbie.
There was a need to process 5-8 large CSV files in RStudio (the tool is not discussed). I started to try and a number of questions arose:
1. How to do it?
2. How to write a loading progressbar?
3. General recommendations?

Somehow a cursory search on the net did not lead to the desired material. Tell me please.