Thank you for the replies. Now I've noticed something weird so maybe you will help to explain this.
As I said, I do not use Google as my default searching engine so, also by default, I have blocked its scripts (coming from google.com and gstatic.com) which are, by the way, also active on gog.com. Yesterday, to check my results in Google I had to unblock these scripts for a while.
Today, to my surprise, I can see not one but two threads connected to my name in Google in the past month - the new one is this one (where I replied having google scripts unblocked at the same time).
So maybe this is the reason why Google can not track me good enough? Maybe Google's search is a "passive" one (it gathers all the info connected to these scripts) and DuckDuckGo is an "active" one (it actually looks itself for the info on the web)?