Yuri Gagarin was the first man to orbit the Earth in a shuttle, according to Google, is this true?

Your father doesn't know everything, and watching pseudo-documentaries on the Science channel or whatever does not make one an expert. The files from that time have been opened, and the early Soviet space program is pretty well documented. There were no deaths on any of the early flights by the initial cosmonaut group. The only man from that group who died did so later in a plane crash after he had be dismissed from the program. These stories of "lost cosmonauts" are based on myths and hoaxes.