Hi @Bhawana ,
I found a video shows you how to send Teams notification using Microsoft Graph, you can see if is helpful to you. The following link also show the components of activity feed notification for your reference.
https://www.youtube.com/watch?v=3MCAKzHkdWU&t=471s
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And please go through this documentation as reference
https://learn.microsoft.com/en-us/graph/teams-send-activityfeednotifications
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