I got a new computer and downloaded gwent card game with steam, it started me over is there a way I can get my old deck I created without starting over from the begining?

Probably involves transferring the save. Probably %appdata% you'll find gwent in one of the directories, copy the contents and place it in your current computer, and your state/saves/achievements should transfer (i hope).

Though it's always possible the saves are in My Documents/My Saves or in the local directory of the game itself (though this seems less likely)