Unfortunately, Polish is not a language that the GoToWebinar platform currently supports. All I can suggest is that you edit the webinar in your account and either reenter the title or copy and paste it in as plain text from a document.
you mean that doing this ("reenter the title or copy and paste it in as plain text from a document") will solve my problem? Unfortunately it still looks the same : - (
But in the webinar description the font is ok, everything looks good. Could you just use the same font as you use in webinar description also in webinar title?