en_tn/col/04/02.md

Continue steadfastly in prayer​

"Keep praying faithfully" or "Keep praying consistently."

for us also

The word "us" refers to Paul and Timothy but not the Colossian believers.

God would open a door

This is an idiom for "God to provide opportunities." (See: rc://en/ta/man/translate/figs-idiom)

mystery of Christ

The message of Jesus Christ that was not understood before Christ came.

Because of that word, I am bound​

"It is for proclaiming the message of Jesus Christ that I am now in prison"

pray that I may make it clear and that I may speak as I ought to speak​

"pray that I might be able to speak the message of Jesus Christ clearly as I should speak."