[Son Nguyen]

Can someone tell me how to figure out what the "other" files are that is taking up so much space?

[Rukbat]

Install a terminal app like Terminal Emulator for Android. Issue the command

df

Look for a line labeled sdcard, emulated or userdata (usually the last line). That's the storage you can use. The rest of storage is partitioned up for different things the system needs, and even with a 512GB phone, you're missing some of it. (If the system partition is 12GB, but the system is using only 8GB, the entire 12GB is unavailable to you. But if the next update gets larger, there's still space for it.)