Need help cleaning my computer and removing unwanted files

I'm looking for a patient IT helper to clean up my desktop and laptop. I want a thorough cleanup of both systems, including removing temporary files, organizing folders, uninstalling unused programs, updating software, and running a basic malware scan. I’d also like advice on best practices for keeping my devices fast and secure. Please confirm you can avoid touching personal data you’re not asked to manage and that you’ll back up anything important if needed. Comfortable with Windows and macOS, and able to explain steps clearly.