Yammer embed

I am quite desperate. For my final project in the company, I have to create my own webparts in SharePoint online. There is a new Yammer webpart in the SharePoint Modern UI and it doesn't have the option to add a scrollbar. That's why I wanted to create my own Yammer webpart. I tried hundreds of code constellation, but I don't get anything besides this: 

This is my render function and the embed code works perfectly on https://www.yammer.com/widget/configure: 

All help is much appreciated!

Kind Regards

David