Because of your being tested and proved by this service

This can be stated in active form. Alternate translation: "Because this service has tested and proven you" (See: rc://en/ta/man/translate/figs-activepassive)

you will also glorify God by obedience ... by the generosity of your gift to them and to everyone

Paul says that the Corinthians will glorify God both by being faithful to Jesus and by giving generously to other believers who have need.