As to your question: Neither you, nor I, nor the world’s best evangelist, nor the Pope can convince someone. That is the job of the Holy Spirit. Our part in all of this is to pray for them, invoking the Holy Spirit, employing patience, and showing them by your life, words and actions, the joy that you have found.
I know that this is not nearly as satisfying as having a killer argument, but that is how the Lord works. Prayer, example and patience.