ESRI-Map visual in PowerBi, edit 3rd party layers

Hello there,

I am actually working on data to be dispayed on a map visual to show customer locations.

The visual is the built-in ESRI-Map Visual.

In there I can add layers to the map, so a regional layer to display administrative areas for germany (Kreise).

Unfortunately the border line of the area is very thick and the fontsize of the long names of the area makes it quite unreadable. I would like to abbreviate names e.g. replacing Long Name ("Düsseldorf") by its related car-plate indicator "D" for all the areas (~400)

My question: Can you recommend a source / a tutorial on how to edit ESRI-Layers without having ESRI-Software avialable.

Thank you very much for your input.

Thomas