en_tn_lite_do_not_use/2co/01/01.md

Paul ... to the church of God that is in Corinth

Your language may have a particular way of introducing the author of a letter and its intended audience. Alternate translation: "I, Paul ... wrote this letter to you, the church of God that is in Corinth"

Timothy our brother

This indicates that both Paul and the Corinthians knew Timothy and considered him to be their spiritual brother.

Achaia

This is the name of a Roman province in the southern part of modern-day Greece. (See: rc://en/ta/man/translate/translate-names)