the former days

"the time in the past"

after you were enlightened

Learning the truth is spoken of as if God shined a light on the person. This can be stated in active form. AT: "after you learned the truth about Christ" (See: rc://en/ta/man/translate/figs-metaphor and rc://en/ta/man/translate/figs-activepassive)

"how much suffering you had to endure"

This can be stated in active form. AT: "People ridiculed you by insulting and persecuting you in public" (See: rc://en/ta/man/translate/figs-activepassive)

"you joined those"

God's eternal blessings are spoken of as a "possession." (See: rc://en/ta/man/translate/figs-metaphor)