You can block any website on the internet, including gstatic.com, by going into your firewall settings and disabling connections for a specific — but you shouldn’t block Gstatic.
If you are having problems with your computer, then chances are they’re not caused by Gstatic. When in doubt, it’s always a good idea to run a full system scan with a secure antivirus to find out if you have any threats harming your PC. If you need to block an unsafe domain with your firewall, Bitdefender’s firewall is really easy to use.