Here pleasing and serving Christ is spoken of as Paul's only purpose for living. Alternate translation: "to go on living is an opportunity to please Christ" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here death is spoken of as "gain." Possible meanings for "gain" are 1) Paul's death will help spread the message of the gospel or 2) Paul will be in a better situation. (See: [[rc://en/ta/man/translate/figs-metaphor]])