Here "grace" refers to God's choosing Paul to be an apostle and leader of the church. You can make this explicit in your translation. You can also translate this in an active form. AT: "because God freely chose me to be an apostle" (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/figs-activepassive]])
Paul implies here that believers have different abilities that correspond to their faith in God. AT: "since God has given each of you different abilities because of your trust in him" (See: [[rc://en/ta/man/translate/figs-explicit]])