How to get the workflow of a change item programmatically?

I agree with you, my query was not yet optimal. The main problem, however, was how I handled the return value. I was reading the individual query parts directly, e.g. var act = workflowProcessActivity.getItemByIndex(0).getProperty("related_id"); That did not work. But with the help of XPath I am able to read the desired values:

var act = workflow.getItemsByXPath("//Item[@type='Activity']");
var actID = act.getItemByIndex(0).getID();

Thank you both for your help!