"To jest zegarek Adama."

Translation: This is Adam's watch.

[Jack.Elliot]

this is the watch of Adam

[karlr42]

..is not a natural English sentence.

If you are going to put the words in that order, I would say "This watch is Adam's".

[MetalCotta]

I know one Adam from Poland. He's cool person, and because of him I'm here!

[alik1989]

Good for you! :)

[Titan4eg]

"This is Adam's handwatch"?