OHMYGODJCABOMB you have already gotten an answer on the Russian Forum. This issue is related to some games that have specific editions. For example, some change publishers and versions over the years, that's why separate product IDs are needed. However, during checkout, you will be informed if you already have said game in your library.

Opening a Forum Thread on General because you are unsatisfied with our answer, and being hostile towards GOG Staff, won't escalate the situation. Please write a Ticket in the future, as that is the proper way to inform Support about problems you might encounter. Also keep in mind that Thread bumping is against our Forum Code of Conduct.