In this verse Paul uses the words "we," "our," and "ourselves" to refer to himself and Timothy and possibly others who served with them. These words do not include the people he was writing to. (See: [[rc://en/ta/man/translate/figs-exclusive]])
Paul uses the word "boasting" ironically here. Boasting is usually a bad thing, but Paul is confident that he has lived "with holiness and godly sincerity" and is telling the Corinthians so. (See: [[rc://en/ta/man/translate/figs-irony]])
Paul speaks of not being guilty as if his conscience were a person that could speak. Alternate translation: "We know by our conscience" (See: [[rc://en/ta/man/translate/figs-personification]])
Here "fleshly" represents human. Alternate translation: "not relying on human wisdom but on the grace of God" (See: [[rc://en/ta/man/translate/figs-metonymy]])