You can translate this double negative in a positive form. Here "these are things" refers to what Christ has accomplished through Paul. Alternate translation: "For the sake of the obedience of the Gentiles, I will only speak of what Christ has accomplished through me in my words and actions and by the power of signs and wonders through the power of the Holy Spirit" (See: [[rc://en/ta/man/translate/figs-doublenegatives]] and [[rc://en/ta/man/translate/figs-explicit]])