This is the time you need a recent system backup. I make backups at least every month to my external H/D. If I get a problem like that, I can be back to a normal system within 3-45 mins. I personally use Acronis TrueImage but there are a number of free programs, though they may take a bit longer ro recover the system. If you have a W8 O/S you can restore your system back without losing your data if you have made backups to a separate disk.
Hands-on: Samsung Galaxy S8 review