When you try to toggle the switch to off, you see the Pause Web & App Activity? prompt.
On the Activity controls page, click the toggle switch next to Web & App Activity to the "off" position.
On the left side of the screen, click the Activity controls selector.
Once you've cleared your address bar history, you can turn off further tracking by disabling the Google omnibox suggestions.
On the confirmation screen, in the lower-right corner, click the button.
In the upper-right corner of the next prompt, check the box next to Select All, and then click the Next button.
In the Delete Activity prompt, click All time.
On the left side of the screen, click the Delete activity by selector.
After that, you can disable omnibox suggestions to prevent them from coming up in the future. To clear your address bar history, you need to use Google's My Activity tool.