is it possible to show the user some loading window to hide the loading of the application behind it when it slows down?
you can always use a css loader in a pop up to overlay the page while something loads but you need to have a condition to show/hide it. For example; when page loaded entirely is no or when RG is loading, a file uploader is loading, etc. I don’t think there is a way to generally to show a loader without a specific condition.