When the handle is broken - it is a spring issue.
Note
There are x2 springs in every Smart Lock's box, you need to use it and follow the steps shown in the video below, it will help you to fix the broken handle.
Warning
If you fixed the spindle and the handle is not fixed, please check the Clutch - it is very durable and made of zinc alloy, so it's likely that unusual force while opening the door may have broken the handle > In this case, you need to replace the clutch.