Memory - what fills it?

I had trouble upgrading to Android 6, then I figured out it was because I had too little memory. But I can not understand what takes up all the memory. Of the 25 GB in the phone, about 2,5 was music, 0,5 photos, 4 is apps. I took away the music and the photos, but what takes the other 20 GB? Is this the way it should be? I have looked at all the other folders, but there is little there.
I did buy a new SD memory card where I now put the music. That seems to work. And I now have almost 2,5 GB available on the main part of the phone.
So this is not an urgent question, just a bit of house-cleaning from an untechnical user who wants to avoid problems in the future. If anyone knows, I am curious.

This topic was automatically closed 182 days after the last reply. New replies are no longer allowed.