en_tn_condensed/act/17/03.md

He was opening the scriptures

Possible meanings are 1) to explain the scriptures in a way that people can understand is spoken of as if Paul were opening something so people can see what is inside of it) or 2) Paul was literally opening a book or scroll and reading from it.

it was necessary

"it was part of God's plan"

to rise again

"to come back to life"

from the dead

From among all those who have died. The expression "the dead" describes all dead people together in the underworld. To come back from among them speaks of becoming alive again.