Encapsulating/Grouping based on TopN

Hi PowerBi Friends,

I have a sample data and wanted to group/encapsulate it based on the TopN given. In addition, I am getting a null value here showing which I think is not good idea to be included as well. Do I need to have a custom table and have a relationship into it? Attached is the sample pbix file which you can play around. Thanks for the help!
https://www.dropbox.com/s/xszrjtxt9oo8k76/sampledata.pbix?dl=0

End Result would be like this