"because of God's will" or "because God wanted it to be this way." Paul became an apostle because God wanted Paul to be an apostle, and not because a human being chose him.
## according to ##
Possible meanings: 1) "in keeping with," meaning that just as God promises that Jesus gives life, he has made Paul an apostle; 2) "for the purpose of," meaning that God appointed Paul to tell others about God's promise of life in Jesus.
## the promise of the life which is in Christ Jesus ##
"God has promised to make those who are in Christ Jesus alive"
## beloved child ##
"dear child" or "child who is loved" or "child whom I love." Timothy was converted to Christ by Paul, and Paul considered him like his own child for this reason.
## Grace, mercy, and peace from ##
"May grace, mercy and peace be yours from" or "May you experience kindness, mercy and peace within from"