Hi Mufeed,
Adding to what Jocelyn said :
Step by step if you go, you can achieve.
1. Get all the workitems in your app by configuring task id.
Detailed steps are given here :
Refer how to guides : 1 to 6.
2. Get the decision outcomes (If the step type is activity you need to activate it by implementing above badi). If user decision, then not required.
Regards,
Tejas