Do you try use ctrl+c and ctrl+v?

Lets try again: first find a word on the page without using the mouse second, Select the word or phrase without using the mouse

ctrl+c and ctrl+v, that I can handle after step 1 & 2

Ctrl+f opens the search in page feature. However, the result is not automatically selected and ready for copying. And since you already typed the query, you wouldn't really save any time that way...

Firefox has some accessibility features you could explore: Accessibility features in Firefox - Make Firefox and web content work for all users. These include placing a movable cursor into the page, or searching/selecting using / and other possibly useful items. Maybe between them you can find a good workflow. If not, maybe an add-on?

Edit: Here's an example of how to select the word accessibility in this post:

Type:

/acce

Press:

Esc, Ctrl+Shift+right

Edit: Actually it works with Ctrl+f as well, and that might be better if the word is common so you can use Next/Previous.

Press:

Ctrl+f

Type:

acce

Press:

Esc, Ctrl+Shift+right

The only way to copy the paragraph that contains the search term is with the mouse (probably a triple click works; pref: browser.triple_click_selects_paragraph).
With the keyboard you can only do this if caret browsing is enabled.