"Know this as the most important thing." See how you translated this in 2 Peter 1:20.
Here the word "desires" refers to sinful desires that are opposed to God's will. AT: "live according to their own sinful desires" (See: rc://en/ta/man/translate/figs-explicit)
The mockers ask this rhetorical question to emphasize that they do not believe that Jesus will return. The word "promise" refers to the fulfillment of the promise that Jesus will return. AT: "The promise that Jesus would return is not true! He will not return!" (See: rc://en/ta/man/translate/figs-rquestion and rc://en/ta/man/translate/figs-metonymy)
Here "fathers" refers to ancestors who lived long ago. "Fell asleep" is an idiom that means they died. (See: rc://en/ta/man/translate/figs-idiom)
The mockers exaggerate with the word "all", and they argue that since nothing in the world has ever changed, it cannot be true that Jesus will return. (See: rc://en/ta/man/translate/figs-hyperbole)
This can be translated as a verbal phrase. AT: "since God created the world" (See: rc://en/ta/man/translate/figs-abstractnouns)