Your private photos are only as secure as your password.
If you are still uncomfortable storing "fotos privadas" on Google’s servers, consider these privacy-first alternatives: Site Drive.google.com Fotos Privadas
Everything in your personal Google Drive is private from others unless you create a shared link or invite someone via email. Google Help Google Photos : Photos are private by default. Your private photos are only as secure as your password
Your "fotos privadas" might actually live in Google Photos but are accessible via Drive. Check drive.google.com and click "Google Photos" in the left sidebar to see your backed-up images. Site Drive.google.com Fotos Privadas