en_tn/2jn/01/12.md

and I did not wish to write them with paper and ink

This can be translated "but I did not want to write them to you in a letter."

face to face

This can be translated "actually with you"

joy may be made full

This can be translated "joy may be complete"

The children of your elect sister

Here John compares this other church to a sister. And the believers that are a part of that church are compared to children. This emphasizes that all believers are a spiritual family. (See: rc://en/ta/man/translate/figs-metaphor)