Walking is a metaphor for living. Alternate translation: "conduct your life in the power of the Holy Spirit" or "live your life in dependence on the Spirit" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The sinful nature is spoken of as if it were a person and wanted to sin. Alternate translation: "what you want to do because of your sinful nature" or "the things you want to do because you are sinful" (See: [[rc://en/ta/man/translate/figs-personification]])