Getting Activity Stream via API


Hello Everybody,
I am new to the Kanboard Discussion Forum. So if I post my question the wrong way, tell me what to do and I will do my best.

->My question:
But now the question. I want to retrieve the activities from a task by API but I can’t find the correct API request to do this. Has someone any idea to deal with that?

-> What I original want to do and why the question comes up for me
The reason why I want to do this is the following. I want to generate metrics for my board. For example I need a Cumulative Flow Diagram or the throughput for a project. To build this metrics I need the dates when a task changes the column. My hope is that I can extract the column change through the activity stream (via API).
If anyone has a better idea to do what I want to do, it would we phantastic if you could give me a hint.

Best wishes from Frankfurt(main) Germany