Hi @marcin246813579 apologies for the late response.
I am also sorry to hear that you are still experiencing FPS drops after reinstalling Windows 10.
Can you confirm if you are only experiencing this issue in Svartalfheim or do you also experience it on other maps? If it is only in Svartalfheim does the FPS drops occur in any specific region or all of them?
I understand that you have already updated Windows and your drivers. Could you also try any of the remaining troubleshooting steps that you may not have tried in our support article here.
I also understand that you are playing with ultra settings, as a test can you try lowering the settings to see if that makes any difference.