[edit] Overleaf guides

[edit] LaTeX Basics

[edit] Mathematics

[edit] Figures and tables

[edit] References and Citations

[edit] Languages

[edit] Document structure

[edit] Formatting

[edit] Fonts

[edit] Presentations

[edit] Commands

[edit] Field specific

[edit] Class files

Yes, you can comment out several lines at once by selecting them and pressing Ctrl-/ (slash) (command-/ on a Mac). You can also use the comment package to comment out large sections of text. Just add

<p>to your preamble, and then use</p>

in the text to create a block comment.

Another option is to enable vi editor mode and use the standard vi commands for commenting.