There are two and one half ways to quote.
The easiest way is to push the quote button (red arrow, below).
The second say is to highlight the text you wish to quote (red arrow, below).
The next step is to page down to “reply” box, and push the “quote” button (red arrow, below).
Then a window pops up to select which quote (there can be several to choose from). If only one choice is available, then click button (black arrow).
The one/half version is once quote is in your “reply” box, you can edit it, before posting (blue arrow).
I do caution that if you edit someones quote, please make note as to what and why it was edited for (spelling, fact correction, etc.)!
Now to shorten the quote, without other edits, that is OK to do.
If this didn’t help, please let me know.
BudW