To explore partitions you may have a glance at you whole disk, how much size you left on each one or when did you modify them, it provides you many new thoughts on arranging data. follow the steps please.
Hidden partitions are not listed in File Explorer when you press Windows + E in Windows 10, but listed in Disk Management when your right-click on Start Menu, some hidden partition can be deleted or extended to system partition, but some are recovery files or boot files in Windows, how to tell the difference? They look the same in Disk Management; free capacity is not the real size.
Use Partition Expert to explore hidden partitions