Adding a slicer by columns

Hello, I am new to Power BI and am having an issue trying to create a slicer to filter through my columns. For example, I have data broken down into a few groups as shown below:

I want to be able to add a slicer to filter through my visuals by column, but there is no option for this. I have tried making a new query and unpivoting the columns such as below:

This, however, is not feasible, since I want to be able to create a stacked barchart visual such as this: 

But when I create my new unpivot column, I cannot use the new 'values' column since I still want my data categorized into the groups. I also lose all my relationships when creating the new unpivoted column. How can I fix this??