The phone has turned on the accessibility menu function. Click the icon to pop up a quick navigation menu. You can turn this feature off in accessibility settings.
Setting path:
realme UI 3.0 and above versions: Settings > System / Additional Settings > Accessibility > Vision > TalkBack > Shortcut > Turn off the Accessibility button.
realme UI 2.0 & 1.0 Setting path:Settings > Additional settings > Accessibility > TalkBack > Shortcut > Turn off the Accessibility button.