macOS sierra scrollbar issue
Go to finder and press command+shift+G on your keyboard and the dialogue box that appears paste in - this path in it 

/Users/your
username/Library/Preferences/com.apple.AppleMultitouchMouse.plist and delete this plist file com.apple.AppleMultitouchMouse.plist then go to system preferences and click on general and instead of selecting appear when scrolling select automatically based on mouse or trackpad