en_tn/2th/02/05.md

Do you not remember ... these things?

Paul uses a rhetorical question to remind them of his teaching when he was with them previously. This can be expressed as a statement. AT: "I am sure you remember ... these things." (See: rc://en/ta/man/translate/figs-rquestion)

these things

This refers to the return of Jesus, the day of the Lord, and the man of lawlessness.

he will be revealed only at the right time

This can be stated in active form. AT: "God will reveal the man of lawlessness when the time is right" (See: rc://en/ta/man/translate/figs-activepassive)

mystery of lawlessness

This refers to a sacred secret that only God knows.

who restrains him

To restrain someone is to hold them back or to keep them from doing what they want to do.