Its the android OS.. and is same everywhere.. you might want to move some photos or videos.. they are taking 112GB of your phone.. mostly 4k videos take alot of space.. try moving them to your pc or hard disk or may be cloud.. cheers..
me too but its 16.1GB on M series and you're on S Series so it maybe on features that your device may have like Knox, fingerprint, face unlock(takes high resolution photos), Android OS(gets higher on Androids new features) etc.