Unfortunately that system dialog is almost useless, as any storage usage that doesn't fall into one of that small handful of categories isn't being shown. Hence it's giving us no clues as to what is using the storage.

So unless that 3 dot menu has a more useful option (I don't have a Samsung, so don't know what their software offers) you really need a better storage analyser. DiskUsage is one that I like: it will provide very detailed analysis of the user-accessible part of your internal storage (if you aren't rooted there are things it can't show you, but at least you'll see the size of things like "system data").

Bear in mind that 10GB or so will be being used by the system software. Most storage displays hide this under "other" or "miscellaneous", though more recently some have actually started showing this explicitly, so it's especially disappointing that your menu doesn't show that. This is why I wonder whether it's worth tapping on the 3 dots in the top-right corner to see whether there are other, more useful, display options.

 

I would ditch the social media apps, and just use my browser for them.
Set a bookmark for each one.
As long as you don't clear cookies, you will stay logged in.

This should save you a great deal of space, as you can now uninstall these apps.

Next, open your file manager, and select DCIM.
Show hidden files, and look for .thumbnails.

If you take or download a lot of pics and videos, this .thumbnails can become huge!

It is preventable, but you may have to change your gallery app.

First, see how big it is and let me know.
If it is being a pig, then I will tell you how to solve that.