Paul begins his letter to the Philippians with praise for them, and then says this now famous verse. “And I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ” (ESV).
It is not that difficult of a verse to translate. The only really question is the translation of en hymin. The “you ” is plural, a fact obscured by the English language. This is partly why some translations prefer “among” instead of “in” since it helps clarify that Paul’s confidence is in God’s work within all the people of the Philippian church.