"Miscellaneous data" isn't a folder. What it is is that your phone tells you your storage usage in a small number of categories, and calls everything else "miscellaneous".
I suggest looking at your apps and sorting by size (many, but not all, versions of Android allow you to do this in Settings > Apps, otherwise you can do it in the Play Store > Installed apps list). This will show you which apps are using the most storage. You may find browsers, social media apps amongst the big users. Select those apps in Settings > Apps and click on the "storage" information, and you'll have the option to clear their caches (which are just temporary files) or their data (so with care, as that will remove all of your settings, preferences, history, messages, etc for that app). My guess, from the way this has filled up, is that it's caches that are your problem - by their nature these will fill constantly.