When you ping address b.gk.sk and you receive No Host Found error, it can be caused multiple things. Below is few workaround/correction for this problem
1) Type cmd to search
2) Click Command Prompt
3) Type ipconfig /flushdns and press enter
4) Wait until you get Successfully flushed message
5) Try to ping again the address if you get the ip, you are good to go, othervise go to next workaround.
1) Type settings to search
2) Click settings
3) Click Network & Internet
4) Click Ethernet (or WLAN)
4) Click Edit next to DNS server assigment
5) Type 1.1.1.1 (Cloudflare) or 8.8.8.8 (Google DNS) to Preferred DNS
and 1.0.0.1 (Cloudflare) or 8.8.4.4 (Google DNS) to Alternate DNS
6) Click Save