Hello @Abduerhman Salama,

Since you are integrating your BPT with CMF,

For assigning an activity to a group a server action called 'Activity_AssignToGroup' is used which you can find inside 'CaseServices_API' module of CMF (take dependency if not already taken).

This action helps you to assign an activity to a group by passing the Activity Id and GroupId.

This action you can perform on the 'OnReady' Event of your HumanActivity.

But, as i read your question you want to assign a single activity to multiple groups, which (as far as my knowledge) not seems correct.

Like how can a request be pending for multiple groups at a time.

Still if that's the requirement then you have to store the GroupId's which user is selecting at runtime in the entity through which BPT is being triggered, then put a decision in the workflow and get the GroupId's selected by the user now iterate over the GroupId list and assign the activity to multiple groups, using the action mentioned above. (again i am not sure it will work as per your requirement )

Thanks & regards 

Anees