The idea of walking is often used for the idea of conducting one's life. Alternate translation: "Live in such a way that those who are not believers will see that you are wise" (See: [[rc://en/ta/man/translate/figs-metaphor]])
To "redeem" something means to restore it to its rightful owner. Here time is spoken of as something that can be restored and used to serve God. Alternate translation: "do the best things you can with your time" or "put the time to its best use" (See: [[rc://en/ta/man/translate/figs-metaphor]])