the whole world

the world Paul and his readers knew and could travel in, which was the Roman Empire

For God is my witness

Paul emphasizes that he earnestly prays for them and that God has seen him praying. The word "for" is often left untranslated.

A person's spirit is the part of him that can know God and believe in him.

The good news (gospel) of the Bible is that the Son of God has given himself as the Savior of the world.

This is an important title for Jesus, the Son of God. (See: rc://en/ta/man/translate/guidelines-sonofgodprinciples)

"I talk to God about you"

"Every time I pray, I ask God that ... I may succeed ... in coming to visit you"

"in whatever way God allows"

"eventually" or "finally"

"because God desires it"