No internet connection on WSL Ubuntu (Windows Subsystem for Linux)

Recently I installed WSL Ubuntu 18.04 on my Windows machine, but nothing seems to work properly, because I have no internet access.
I tried a few commands and sudo apt update says 'Connection failed' and ping google.com literally takes forever as you can see in this screenshot:

I also checked nano /etc/resolv.conf and made sure that the nameservers are right, completely disabled Kaspersky and its firewall, disabled Hyper-V, reinstalled WSL a few times and even disabled Windows Defender. Nothing helped.

So do you have any ideas what the issue could be here?

Open Command Prompt as an Administrator and type these commands:

netsh winsock reset 
netsh int ip reset all
netsh winhttp reset proxy
ipconfig /flushdns

Reboot your machine.

https://github.com/microsoft/WSL/issues/3438#issuecomment-410518578