While software does take up some space 20GB is excessive. if you dont mind follow the steps below to see where the storage is going
if other apps is using unecessary space an app may be defective @Bdubzx8
With any operating system set up on a phone, a certain amount of storage is reserved and used so the phone can run optimally. If you go into device care and storage and it should give you a breakdown of where the storage is being allocated to.
You stated "Others is at 17GB" some times that can be due to hidden files or items not completely erased or sometimes large apps storage. First lets start with clearing out the trash folder.
1.Find the gallery app
2. Select the 3dots in the right corner
3. Select Trash
*these are items that you deleted but are still taking up space on the device. If you are sure you want to delete these items select to empty trash.
The next step would be checking apps:
3. Select the 3dots in the upper right corner
4. Sort by size
5. Here is where you can see what apps are using too much storage.