You can look up what data like this gets copied from your phone to Google's servers in your Android smartphone's settings. Go to settings/accounts/Google, and you'll also find the options to deactivate synchronisation in each category.
Anyone who's wondering how photos and videos end up on Google servers even though there's no category for them under "account" should have a look in the settings of their Google photo app.
That's where you can switch off the synchronisation feature, meaning photos and videos are stored only on your smartphone. – dpa