Hi, jb64, thank for your help. Your post was very useful.
But, I have some questions about the support article that you mentioned:
1) If was really the Time Machine snapshots the cause of the huge system storage, why my Finder window include local snapshots in their calculations of the storage space available on a disk, as you can see below? The amount is the same of "About This Mac". This seems not right.
2) I'm not a IT guy (actually, I'm a lawyer), but, if I understood correctly, sometimes the OS uses speed of SSD (instead use memory). This action of macOS storage snapshots does not make the MacBook be slow?
Anyway, I schedule a call with AppleSupport to see this matters more accurately and after orientation I'll post the proper informations here.