My Samsung S5 with Android 6.0.1 has not enough storage memory. By default, it has 16GB available of which 4.2GB is used by the system (according to the "Storage" information page in the settings). My phone says, I'm using around 10GB of storage memory.
Up to this point, I moved almost everything except for some very small apps to my SD card and removed this SD card from my phone, so it's content won't show up in the stats.
To find out which places eat the most storage memory, I used a File Manager app from the App Store ("File Manager") which can access the root folder of my device. It turns out that the folder /storage/emulated/0 (the place which you can examine using the default file manager) only takes up around 4GB!
However, the other folders in the root folder only contain very small data in the range of megabytes.
How can I examine where these 6GB went?!
By the way, of course, I deleted all cache files which I can delete, I even deleted the logs from *#9900#.