Peter finishes instructing the believers and ends his letter.
since you know about these things
"These things" refers to the truths about the patience of God and the teachings of these false teachers.
so that you are not led astray by the deceit of lawless people
"Led astray" here is a metaphor, as if they have moved from the correct path onto the wrong path. This can be stated in active form. AT: "so that lawless people do no lead you in the wrong direction with their deceitful words" (See: rc://en/ta/man/translate/figs-activepassive) (See: rc://en/ta/man/translate/figs-metaphor)
led astray ... deceit
Being persuaded to disobey God is spoken of as it were being led off the right path to follow. Deceitful or false teachings are spoken of as if they were someone who could lead another person off the right path. (See: rc://en/ta/man/translate/figs-metaphor)
you lose your own faithfulness
Faithfulness is spoken of as if it were a possession that believers could lose. AT: "you stop being faithful" (See: rc://en/ta/man/translate/figs-metaphor)
grow in the grace and knowledge of our Lord and Savior Jesus Christ
Here growing in the grace and knowledge of the Lord represents experiencing his grace more and knowing him more. The abstract noun "grace" can be expressed with the phrase "act kindly." AT: "receive more of the grace of our Lord and Savior Jesus Christ, and know him more" or "be more aware of how our Lord and Savior Jesus Christ acts kindly toward you, and know him better" (See: rc://en/ta/man/translate/figs-metaphor and rc://en/ta/man/translate/figs-abstractnouns)