"I know everything about that man."
Translation:O tamhletom muži vím všechno.
Approximate analogies of Czech demonstratives with English:
O tom muži - about the/that man
O tamtom muži - about that man there
O tamhletom muži - about that man over there
O tomto muži - about this man (formally)
O tomhle muži - about this man
O tomhletom muži - about this man here
And then there are also several dialectal versions like "o tadytom", "o tutom", "o hentom", "o tomdlectom", "o támletom" etc. :)