Hi, @Philipp.
I looked at the files in your deploy and Netlify will not use the pre-compressed versions (the MyApp.dll.br version) because the request the browser makes does not include that file extension. This pre-compression of files is something people often try to get working at Netlify but we simply just do not support it out of the box.
There is another thread where people discuss the possibility of doing this using edge functions here:
You can do this manually by writing custom edge functions.
Would using your version save 20% of the bandwidth used for transferring that file? Yes, it would. However, Netlify is not designed to do this and getting that working is non-trivial. That said, it can be done and the effort required is not herculean either.
The point that I am making is that this 20% difference for this file is likely not going to be a game changer for this site. It could be but probably not.
Is the saving of 68 KB per site load worth spending the time coding a custom solution for this? I personally would not spend time working on that but my priorities may differ from yours. Please feel free to use an edge function to accomplish this if you want to do so.
If you have questions about using edge functions to make Netlify use the pre-compressed version, please let us know. (There are some details and an example edge function in the post above.)