Christ was chosen

This can be stated in active form. AT: "God chose Christ" (See: rc://en/ta/man/translate/figs-activepassive)

before the foundation of the world

You can translate this with a verbal phrase. AT: "before God created the world" (See: rc://en/ta/man/translate/figs-abstractnouns)

This can be stated in active form. AT: "God has revealed him to you" (See: rc://en/ta/man/translate/figs-activepassive)

Peter does not mean that his readers actually saw Christ, but that they learned the truth about him. (See: rc://en/ta/man/translate/figs-metaphor)

"and glorified him" or "and showed that he is glorious" (See: rc://en/ta/man/translate/figs-abstractnouns)