en_tn/1jn/02/07.md

Beloved

This can be translated as "Friends" or "Dear believers in Christ"

I do not write a new commandment to you, but an old commandment

John was referring to Jesus' command to love one another. This could be translated as "I am writing to you to love one other. That is not a new thing to do but an old commandment that you were told."

from the beginning

"from when you first believed in Christ" (See: rc://en/ta/man/translate/figs-explicit)

Yet I am writing a new commandment to you

This can be translated as "But in one way the commandment I write to you is new."

which is true in Christ and in you

This can be translated as "It is new because what Christ did was new, and what you are doing is new."

the darkness is passing away and the true light is already shining

Here "darkness" refers to evil and "light" refers to goodness. This can be translated as "because you are ceasing to do evil and you are doing more and more good." (See: rc://en/ta/man/translate/figs-metaphor)