Don't worry, Sergey, and don't take it personally. Whatever you do, there'll always be someone who feels the need to criticise it. This is an unpleasant side of human nature that is particularly evident on the internet. There's no need to apologise for your question.
Your question "Who was the first man in space?" is fine. And as far as I know, Gagarin is universally recognised as the first man in space. It's one of those general knowledge questions that everyone knows..the highest mountain, the longest river, and the first man in space.