Not any security software is installed, only avast free installed. Auto update is enabled weekly.
scan runs without lag, just internet browsing problem.
ping returns fine.
tracert returns fine.
DNS, nslookup returns fine.
Only internet browser opens website slow. disable/enable avast fixes problem temporarily. Later the problem happens again.
playing with internet options, clearing browsing history, connection type, same result comparing to untouched computers with avast free.
I tested for 3 months because I have lots of time to see how it works patiently with both physical pcs and virtual machines and didn't want to conclude quickly it's avast. I uninstalled avast on all machines, now without counting seconds which takes to open websites I have on my testing list, I can easily feel it's superfast, same as I installed windows os.
Instead of telling me why I hate avast, tell their team to do something. I'm here to tell my experience with environment which I think it's too hard for anyone to blame my system problem.