Verify if the portal is set to Slovak language: http://www.truni.sk/en/changing-portal-language-setting.
Click on the Cancel button when entering the security questions and answers, and chose the Password Recovery option. Repeat this action until questions you can answer appear. If you forgot answers to all your security questions, use these instructions.
After password recovery log into the portal and set up your security questions and answers again. Choose questions you can remember without noting them down. Pay special attention to optional question, form it so the answer is straightforward and easily to remember for you. In emergency case one answer to one question is satisfactory for password recovery (as stated in these instructions).