doesn't hide dock bar automatically in High Sierra

I set option "automatically hide and show the dock" for dock bar but to hide it I have to move pointer in bottom side of screen and to move it more times to this direction, otherwise dock is always shown. After this behaviour, dock automatically hide for opened application and It's ok. If I open new app or I switch to another app behaviour problem returns again I have to move pointer again to bottom more times to hide dock.
How can I solve it please?
Are you sure it is properly activated on your system settings? Most versions of Mac OS X contains the same settings, but sometimes the toggle in System Preferences looks slightly different in past versions of Mac OS X, because there are less options available to customize the Dock experience in general. To activate it using keyboard shortcuts, just hit Command+Option+D at any time, and the dock will glide away or back again.